Security hardening from the assessment; testing fixes

Security (ultimo-security-report.md):
- Security headers on every response, the app shell included: they lived at
  server level and nginx dropped them in any location with its own header.
  CSP, framing, nosniff, referrer, permissions (docker/nginx-security.conf).
- Plain HTTP forwarded by the reverse proxy is redirected to HTTPS; HSTS on
  HTTPS responses. server_tokens off.
- Cross-site state-changing /api requests refused (login CSRF), WebSocket too.
- Validation errors in the usual error shape, without the request model.
- New-password policy: max 128, common/own-address/repeated refused,
  breached-password check (HIBP k-anonymity, fails open).
- Message HTML: links keep only http(s)/mailto (sanitizer v6); the HTML
  endpoint carries its own no-script CSP.
- Outbound fetches pinned to the checked IP (DNS rebinding); external
  IMAP/SMTP servers re-checked before each connection; CGNAT and mapped
  addresses counted as non-public.

Fixes from testing:
- IDLE loop catches up before idling: mail that came while the worker was
  away no longer waits up to 10 minutes.
- Restore from Spam/Trash/Archive moves only the removed messages, not your
  reply in Sent.
- Narrow desktop list stacks sender/subject/snippet (subject was squeezed
  to nothing at the default width), with hover actions.
- Phone: wide emails scale to fit the screen.
- Singular forms ("1 message"); no zip button for a single attachment;
  app passwords no longer claim "never used" for mail apps.
- ruff format across the backend.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

backend/app/accounts/discovery.py

@@ -125,9 +125,7 @@ def parse_autoconfig_xml(xml_text: str) -> CandidateConfig | None:
     smtp = _server("outgoingServer", "smtp")
     if imap is None or smtp is None:
         return None
-    return CandidateConfig(
+    return CandidateConfig(imap, smtp, "autoconfig", auth_strategy=_strategy_from_auth(imap.auth))
-        imap, smtp, "autoconfig", auth_strategy=_strategy_from_auth(imap.auth)
-    )
 
 
 # --- DNS SRV (RFC 6186) ------------------------------------------------------

backend/app/accounts/ssrf.py

@@ -2,9 +2,10 @@
 
 All autodiscovery HTTP is HTTPS-only, 5 s timeout, response capped at 256 KB, no
 off-domain redirects, and the target host must resolve exclusively to public IPs
-(reject private/loopback/link-local/reserved ranges). A residual TOCTOU gap
+(reject private/loopback/link-local/reserved ranges). The request then goes to
-(DNS rebinding between our resolve and httpx's own resolve) is accepted for M1;
+the very address that was checked — the name is not looked up a second time —
-a pinned-IP transport can close it later.
+so a DNS answer that changes in between (DNS rebinding) cannot point it inward.
+TLS is still verified against the host name.
 """
 
 from __future__ import annotations
@@ -26,15 +27,12 @@ class SsrfError(Exception):
 
 
 def _is_public_ip(ip: str) -> bool:
-    addr = ipaddress.ip_address(ip)
+    addr = ipaddress.ip_address(ip.split("%", 1)[0])  # drop an IPv6 zone index
-    return not (
+    if isinstance(addr, ipaddress.IPv6Address) and addr.ipv4_mapped is not None:
-        addr.is_private
+        addr = addr.ipv4_mapped  # ::ffff:127.0.0.1 is 127.0.0.1
-        or addr.is_loopback
+    # is_global: not private, loopback, link-local, reserved, unspecified, nor
-        or addr.is_link_local
+    # shared/carrier-grade NAT (100.64.0.0/10, which is_private misses).
-        or addr.is_multicast
+    return addr.is_global and not addr.is_multicast
-        or addr.is_reserved
-        or addr.is_unspecified
-    )
 
 
 async def _resolve_all(host: str) -> list[str]:
@@ -43,8 +41,10 @@ async def _resolve_all(host: str) -> list[str]:
     return [info[4][0] for info in infos]
 
 
-async def assert_host_is_public(host: str) -> None:
+async def assert_host_is_public(host: str) -> list[str]:
-    """Resolve ``host`` and reject if any address is non-public (SPEC §10.6)."""
+    """Resolve ``host`` and reject if any address is non-public (SPEC §10.6).
+
+    Returns the addresses checked, for the caller to connect to."""
     try:
         addresses = await _resolve_all(host)
     except socket.gaierror as exc:
@@ -54,6 +54,31 @@ async def assert_host_is_public(host: str) -> None:
     for ip in addresses:
         if not _is_public_ip(ip):
             raise SsrfError(f"{host} resolves to non-public address {ip}")
+    return addresses
+
+
+async def _pinned(url: str) -> tuple[str, dict[str, str], dict[str, str]]:
+    """``url`` aimed at the address just checked: (url, headers, extensions).
+
+    The URL names the IP, the Host header keeps the name (virtual hosting), and
+    TLS gets the name for SNI and for checking the certificate."""
+    parts = urlsplit(url)
+    if parts.scheme != "https":
+        raise SsrfError("only https is permitted")
+    hostname = parts.hostname
+    if not hostname:
+        raise SsrfError("missing host")
+    addresses = await assert_host_is_public(hostname)
+    # IPv4 first: containers often have no IPv6 route, though DNS returns AAAA.
+    ip = next((a for a in addresses if ":" not in a), addresses[0])
+    literal = f"[{ip}]" if ":" in ip else ip
+    netloc = f"{literal}:{parts.port}" if parts.port else literal
+    host_header = f"{hostname}:{parts.port}" if parts.port else hostname
+    return (
+        parts._replace(netloc=netloc).geturl(),
+        {"Host": host_header},
+        {"sni_hostname": hostname},
+    )
 
 
 async def guarded_get(url: str) -> str | None:
@@ -63,12 +88,7 @@ async def guarded_get(url: str) -> str | None:
     (any non-200 response). Raises :class:`SsrfError` on a policy violation
     (bad scheme, private IP, oversize); lets httpx network errors propagate.
     """
-    parts = urlsplit(url)
+    target, pin_headers, extensions = await _pinned(url)
-    if parts.scheme != "https":
-        raise SsrfError("only https is permitted")
-    if not parts.hostname:
-        raise SsrfError("missing host")
-    await assert_host_is_public(parts.hostname)
 
     async with (
         httpx.AsyncClient(
@@ -76,7 +96,7 @@ async def guarded_get(url: str) -> str | None:
             timeout=HTTP_TIMEOUT,
             headers={"User-Agent": "webmail-autodiscovery/1.0"},
         ) as client,
-        client.stream("GET", url) as resp,
+        client.stream("GET", target, headers=pin_headers, extensions=extensions) as resp,
     ):
         if resp.status_code != 200:
             return None
@@ -114,16 +134,17 @@ async def guarded_request(
     fetch ICS feeds. HTTPS-only, public host required, no off-domain redirects, body
     capped at ``max_bytes``. ``auth`` is an (user, password) basic-auth pair. Returns
     status + headers + body (all statuses; the caller decides what's an error)."""
-    parts = urlsplit(url)
+    target, pin_headers, extensions = await _pinned(url)
-    if parts.scheme != "https":
-        raise SsrfError("only https is permitted")
-    if not parts.hostname:
-        raise SsrfError("missing host")
-    await assert_host_is_public(parts.hostname)
 
     async with (
         httpx.AsyncClient(follow_redirects=False, timeout=timeout, auth=auth) as client,
-        client.stream(method, url, headers=headers, content=content) as resp,
+        client.stream(
+            method,
+            target,
+            headers={**(headers or {}), **pin_headers},
+            content=content,
+            extensions=extensions,
+        ) as resp,
     ):
         chunks: list[bytes] = []
         total = 0

backend/app/accounts/testing.py

@@ -89,6 +89,7 @@ async def test_account(
             smtp_tls=smtp.tls,
             username=username,
             password=password,
+            public_only=True,
         )
     )
     try:

backend/app/api/actions.py

@@ -125,9 +125,7 @@ async def mark_all_read(
         return {"changed": 0}
     messages = list(
         await db.scalars(
-            select(Message).where(
+            select(Message).where(Message.thread_id.in_(thread_ids), Message.user_id == user.id)
-                Message.thread_id.in_(thread_ids), Message.user_id == user.id
-            )
         )
     )
     add, remove = sanitize_flags(["\\Seen"]), sanitize_flags([])
@@ -137,9 +135,7 @@ async def mark_all_read(
     await _push_and_publish(user.id, changed, add, remove)
     bus = get_event_bus()
     for tid in thread_ids:
-        await bus.publish(
+        await bus.publish("thread.updated", {"user_id": str(user.id), "thread_id": str(tid)})
-            "thread.updated", {"user_id": str(user.id), "thread_id": str(tid)}
-        )
     return {"changed": len(changed)}
 
 

backend/app/api/errors.py

@@ -5,6 +5,7 @@ from __future__ import annotations
 from typing import NoReturn
 
 from fastapi import FastAPI, HTTPException, Request
+from fastapi.exceptions import RequestValidationError
 from fastapi.responses import JSONResponse
 from starlette.exceptions import HTTPException as StarletteHTTPException
 
@@ -29,7 +30,23 @@ async def _handler(request: Request, exc: StarletteHTTPException) -> JSONRespons
     return JSONResponse(status_code=exc.status_code, content=body, headers=headers)
 
 
+async def _validation_handler(request: Request, exc: RequestValidationError) -> JSONResponse:
+    """A malformed request, in the usual error shape. Names the first field at
+    fault and what is wrong with it — enough to show the user — but not the
+    whole request model the framework's own answer would spell out."""
+    errors = exc.errors()
+    first = errors[0] if errors else {}
+    loc = [str(p) for p in first.get("loc", ()) if p not in ("body", "query", "path")]
+    field = loc[-1] if loc else ""
+    reason = str(first.get("msg", "invalid value"))
+    message = f"{field}: {reason}" if field else reason
+    return JSONResponse(
+        status_code=422, content={"error": {"code": "validation_error", "message": message}}
+    )
+
+
 def register_error_handlers(app: FastAPI) -> None:
     """Install the error-shape handler for all HTTP exceptions."""
     app.add_exception_handler(StarletteHTTPException, _handler)  # type: ignore[arg-type]
     app.add_exception_handler(HTTPException, _handler)  # type: ignore[arg-type]
+    app.add_exception_handler(RequestValidationError, _validation_handler)  # type: ignore[arg-type]

backend/app/api/messages.py

@@ -88,6 +88,23 @@ def _wrap(fragment: str) -> str:
     return _DOC_TEMPLATE.format(body=fragment)
 
 
+# The sanitized message as a document of its own. The app shows it in a
+# sandboxed frame (frontend MessageBody), but this URL can also be opened
+# directly in a tab, on our own origin: there, this policy is what keeps any
+# script the sanitizer might ever miss from running — no scripts, no plugins,
+# no forms, a sandbox of its own origin, and nothing framing it elsewhere.
+_MESSAGE_CSP = (
+    "default-src 'none'; script-src 'none'; object-src 'none'; base-uri 'none'; "
+    "form-action 'none'; frame-ancestors 'self'; img-src 'self' data: https: http:; "
+    "style-src 'self' 'unsafe-inline'; font-src 'self' data: https:; media-src 'self'; "
+    "sandbox allow-popups allow-popups-to-escape-sandbox"
+)
+
+
+def _html(document: str) -> HTMLResponse:
+    return HTMLResponse(content=document, headers={"Content-Security-Policy": _MESSAGE_CSP})
+
+
 async def _owned_message(db: AsyncSession, user_id: uuid.UUID, message_id: uuid.UUID) -> Message:
     msg = await db.scalar(
         select(Message).where(Message.id == message_id, Message.user_id == user_id)
@@ -123,7 +140,7 @@ async def message_html(
 
     stale = html_part is not None and html_part.sanitizer_v < SANITIZER_VERSION
     if html_part is not None and not allow_remote and not stale:
-        return HTMLResponse(content=_wrap(html_part.content))
+        return _html(_wrap(html_part.content))
 
     # Re-sanitize the original HTML (image-approved sender, or a stale stored copy).
     # If the raw blob is unavailable, fall back to whatever is already stored.
@@ -142,13 +159,13 @@ async def message_html(
                     html_part.content = result.html  # persist the upgraded sanitization
                     html_part.sanitizer_v = result.sanitizer_v
                     await db.commit()
-                return HTMLResponse(content=_wrap(result.html))
+                return _html(_wrap(result.html))
 
     if html_part is not None:
-        return HTMLResponse(content=_wrap(html_part.content))
+        return _html(_wrap(html_part.content))
     text_part = next((p for p in parts if p.kind == "text"), None)
     body = html_lib.escape(text_part.content) if text_part else ""
-    return HTMLResponse(content=_wrap(f'<div class="wm-plaintext">{body}</div>'))
+    return _html(_wrap(f'<div class="wm-plaintext">{body}</div>'))
 
 
 @router.post("/{message_id}/allow-remote-images", dependencies=[Depends(require_csrf)])

backend/app/config.py

@@ -71,6 +71,9 @@ class Settings(BaseSettings):
     # Spelling and grammar checking in the compose window (LanguageTool server,
     # e.g. http://languagetool:8010). Empty: the check is off for everyone.
     languagetool_url: str = Field(default="", alias="LANGUAGETOOL_URL")
+    # New passwords are checked against known data breaches (Have I Been Pwned's
+    # k-anonymity range API: only 5 hex digits of a SHA-1 leave the server).
+    password_breach_check: bool = Field(default=True, alias="PASSWORD_BREACH_CHECK")
     # Auto-purge Trash/Spam messages older than this many days (0 disables).
     trash_retention_days: int = Field(default=30, alias="TRASH_RETENTION_DAYS")
 

backend/app/identity/password_policy.py

@@ -0,0 +1,145 @@
+"""What a new account password must not be (sign-up and reset).
+
+Length is bounded by the request schemas (8–128). On top of that a password is
+refused when it is one of the passwords every guessing attack tries first, is
+made of the user's own address, is one character repeated, or has turned up in
+a known data breach. The breach check asks Have I Been Pwned's range API with
+the first five hex digits of the password's SHA-1 only (k-anonymity: neither the
+password nor its hash leaves the server) and is skipped, not failed, when that
+service cannot be reached — a sign-up never hangs on someone else's outage.
+Set ``PASSWORD_BREACH_CHECK=false`` to never ask it.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import logging
+
+import httpx
+
+from app.config import get_settings
+
+logger = logging.getLogger(__name__)
+
+MIN_LENGTH = 8
+MAX_LENGTH = 128
+
+_RANGE_API = "https://api.pwnedpasswords.com/range/"
+_TIMEOUT = 3.0
+
+# The front of every guessing list (and of every breach), lower-cased.
+_COMMON = frozenset(
+    {
+        "password",
+        "password1",
+        "password12",
+        "password123",
+        "password1234",
+        "passw0rd",
+        "p@ssw0rd",
+        "p@ssword",
+        "12345678",
+        "123456789",
+        "1234567890",
+        "0123456789",
+        "87654321",
+        "11111111",
+        "00000000",
+        "12341234",
+        "qwertyui",
+        "qwerty123",
+        "qwerty1234",
+        "qwertyuiop",
+        "1q2w3e4r",
+        "1q2w3e4r5t",
+        "1qaz2wsx",
+        "zaq12wsx",
+        "asdfghjk",
+        "asdfasdf",
+        "iloveyou",
+        "iloveyou1",
+        "sunshine",
+        "princess",
+        "football",
+        "baseball",
+        "welcome1",
+        "welcome123",
+        "letmein1",
+        "trustno1",
+        "superman",
+        "batman123",
+        "dragon123",
+        "monkey123",
+        "abc12345",
+        "abcd1234",
+        "aa123456",
+        "qazwsxedc",
+        "changeme",
+        "changeme1",
+        "administrator",
+        "admin123",
+        "adminadmin",
+        "computer",
+        "internet",
+        "whatever",
+        "starwars",
+        "michelle",
+        "jennifer",
+        "charlie1",
+        "zaq1zaq1",
+        "haslo123",
+        "polska123",
+        "kochamcie",
+        "zaq1@wsx",
+        "qwerty12",
+        "1234qwer",
+        "q1w2e3r4",
+    }
+)
+
+
+class PasswordRejected(Exception):
+    """The password may not be used; ``code`` and ``message`` say why."""
+
+    def __init__(self, code: str, message: str) -> None:
+        super().__init__(message)
+        self.code = code
+        self.message = message
+
+
+async def _breached(password: str) -> bool:
+    digest = hashlib.sha1(password.encode("utf-8")).hexdigest().upper()  # noqa: S324 - HIBP's format
+    prefix, suffix = digest[:5], digest[5:]
+    try:
+        async with httpx.AsyncClient(timeout=_TIMEOUT) as client:
+            resp = await client.get(_RANGE_API + prefix, headers={"Add-Padding": "true"})
+            resp.raise_for_status()
+    except httpx.HTTPError as exc:
+        logger.warning("breached-password check skipped: %s", exc)
+        return False
+    for line in resp.text.splitlines():
+        candidate, _, count = line.partition(":")
+        if candidate.strip() == suffix and count.strip() not in ("", "0"):  # padding rows say 0
+            return True
+    return False
+
+
+async def check_new_password(password: str, handle: str) -> None:
+    """Raise :class:`PasswordRejected` if ``password`` may not be used by ``handle``."""
+    lowered = password.lower()
+    if len(set(password)) <= 2:
+        raise PasswordRejected("weak_password", "this password is too easy to guess")
+    if lowered in _COMMON:
+        raise PasswordRejected("weak_password", "this is one of the most common passwords")
+    localpart = handle.split("@", 1)[0].lower()
+    if len(localpart) >= 3 and localpart in lowered:
+        # The name with a year or a few characters added ("jsmith2026") is the
+        # first thing anyone who knows the address will try.
+        rest = lowered.replace(localpart, "", 1)
+        if len(rest) < 4 or all(not c.isalpha() for c in rest):
+            raise PasswordRejected("weak_password", "the password must not be your address")
+    if get_settings().password_breach_check and await _breached(password):
+        raise PasswordRejected(
+            "breached_password",
+            "this password has appeared in a data breach — please choose another",
+        )

backend/app/identity/routes.py

@@ -27,6 +27,7 @@ from app.identity.cookies import (
 )
 from app.identity.deps import CurrentSession, CurrentUser, require_csrf
 from app.identity.mailer import MailerConfig, MailerError, mailer_config, reset_mail, send_mail
+from app.identity.password_policy import PasswordRejected, check_new_password
 from app.identity.passwords import hash_password, verify_password
 from app.identity.reset import (
     consume_token,
@@ -125,6 +126,10 @@ _REGISTRATION_ERROR_STATUS = {"handle_taken": 409, "registration_closed": 403}
 async def register(
     body: RegisterRequest, request: Request, response: Response, db: DbSession
 ) -> UserOut:
+    try:
+        await check_new_password(body.password, resolve_handle(body.localpart))
+    except PasswordRejected as exc:
+        raise_api_error(400, exc.code, exc.message)
     try:
         user = await register_user(
             db,
@@ -312,6 +317,11 @@ async def password_reset(body: PasswordResetIn, db: DbSession) -> MessageOut:
     user = await db.get(User, user_id) if user_id else None
     if user is None:
         raise_api_error(400, "invalid_token", "this link is invalid or has expired")
+    # Before the 2FA code and the link are spent: a refused password costs neither.
+    try:
+        await check_new_password(body.password, user.handle)
+    except PasswordRejected as exc:
+        raise_api_error(400, exc.code, exc.message)
     if user.totp_secret is not None:
         if not body.totp:
             raise_api_error(401, "totp_required", "a 2FA code is required")

backend/app/identity/schemas.py

@@ -10,7 +10,7 @@ from pydantic import BaseModel, Field
 
 class RegisterRequest(BaseModel):
     localpart: str = Field(min_length=3, max_length=30)
-    password: str = Field(min_length=8, max_length=1024)
+    password: str = Field(min_length=8, max_length=128)
     recovery_email: str | None = None
 
 
@@ -49,7 +49,7 @@ class PasswordResetRequestIn(BaseModel):
 
 class PasswordResetIn(BaseModel):
     token: str = Field(min_length=1)
-    password: str = Field(min_length=8, max_length=1024)
+    password: str = Field(min_length=8, max_length=128)
     totp: str | None = None  # required when the account has 2FA enabled
 
 

backend/app/indexer/sanitize.py

@@ -18,7 +18,8 @@ import nh3
 # Bump when the sanitization policy changes; body_parts.sanitizer_v records it so a
 # render re-sanitizes stale content from the raw blob (SPEC §10.4).
 # v5: this server's own inline-image URLs quoted in a message load from here.
-SANITIZER_VERSION = 5
+# v6: links keep only http(s) and mailto (no data: pages).
+SANITIZER_VERSION = 6
 
 # This server's inline-image URL, however it ended up written: "/api/…",
 # "https://host/api/…", or mangled to "http:///api/…" by an earlier copy.
@@ -202,6 +203,11 @@ def sanitize_html(
             return _sanitize_style(value, allow_remote_images)
         if tag == "a" and attr == "target":
             return "_blank"
+        if attr == "href":
+            # A link goes to the web or to a mail address: data: (a page made
+            # up by the sender) and cid: are kept for inline images only.
+            scheme = value.strip().lower().split(":", 1)[0] if ":" in value else ""
+            return value if scheme in ("", "http", "https", "mailto") else None
         if tag == "img" and attr == "src":
             lowered = value.strip().lower()
             if lowered.startswith("cid:"):

backend/app/main.py

@@ -37,6 +37,10 @@ def create_app() -> FastAPI:
 
     register_error_handlers(app)
 
+    from app.security.cross_site import CrossSiteGuard
+
+    app.add_middleware(CrossSiteGuard)
+
     @app.get("/api/healthz")
     async def healthz() -> dict[str, str]:
         """Liveness/readiness probe: checks DB and Redis (dev-setup §6)."""

backend/app/models.py

@@ -168,9 +168,7 @@ class Mailbox(Base):
     # IMAP ids are unsigned 32-bit (MODSEQ 63-bit): bigint, not integer.
     uidvalidity: Mapped[int] = mapped_column(BigInteger, nullable=False, server_default=text("0"))
     highestmodseq: Mapped[int | None] = mapped_column(BigInteger)
-    last_seen_uid: Mapped[int] = mapped_column(
+    last_seen_uid: Mapped[int] = mapped_column(BigInteger, nullable=False, server_default=text("0"))
-        BigInteger, nullable=False, server_default=text("0")
-    )
 
 
 class Thread(Base):

backend/app/plugins/http.py

@@ -21,9 +21,7 @@ class PluginHttp:
         content: bytes | str | None = None,
         auth: tuple[str, str] | None = None,
     ) -> GuardedResponse:
-        return await guarded_request(
+        return await guarded_request(method, url, headers=headers, content=content, auth=auth)
-            method, url, headers=headers, content=content, auth=auth
-        )
 
     async def get(self, url: str, **kw: object) -> GuardedResponse:
         return await self.request("GET", url, **kw)  # type: ignore[arg-type]

backend/app/providers/imap_smtp/provider.py

@@ -122,6 +122,16 @@ def _date_criteria(since: date | None, before: date | None) -> str:
     return " ".join(parts) if parts else "ALL"
 
 
+async def _require_public(host: str) -> None:
+    """Refuse a user-named server that now resolves to a non-public address."""
+    from app.accounts.ssrf import SsrfError, assert_host_is_public
+
+    try:
+        await assert_host_is_public(host)
+    except SsrfError as exc:
+        raise ProviderConnectError(f"refusing to connect to {host}: {exc}") from exc
+
+
 @dataclass(frozen=True)
 class ProviderConfig:
     imap_host: str
@@ -138,6 +148,10 @@ class ProviderConfig:
     # The hosted mail server: every user's mailbox is on that one host, so the
     # per-host connection cap (which spares outside providers) does not apply.
     internal: bool = False
+    # A server the user named (every external account): its name is checked
+    # again before each connection, so DNS changed after the account was added
+    # cannot turn the worker on the internal network (DNS rebinding).
+    public_only: bool = False
 
 
 class ImapSmtpProvider(MailProvider):
@@ -196,6 +210,8 @@ class ImapSmtpProvider(MailProvider):
         if self._imap is not None:
             return self._imap
         cfg = self._cfg
+        if cfg.public_only:
+            await _require_public(cfg.imap_host)
         await self._acquire_conn_slots()
         try:
             try:
@@ -540,6 +556,8 @@ class ImapSmtpProvider(MailProvider):
 
     async def send(self, raw: bytes, envelope_from: str, envelope_to: list[str]) -> None:
         cfg = self._cfg
+        if cfg.public_only:
+            await _require_public(cfg.smtp_host)
         use_tls = cfg.smtp_tls == "ssl"
         start_tls = cfg.smtp_tls == "starttls"
         host_slot = (

backend/app/security/cross_site.py

@@ -0,0 +1,91 @@
+"""Refuse state-changing API requests that another web site makes a browser send.
+
+The double-submit CSRF token (app/identity/deps.py ``require_csrf``) guards
+everything a signed-in user can change. The requests made before anyone is
+signed in — sign-in itself, sign-up, a password reset — have no token yet, so a
+hostile page could make a visitor's browser sign in to an account of the
+attacker's choosing (login CSRF): whatever the victim then writes, files or
+uploads lands in the attacker's account.
+
+Browsers say where a request comes from: ``Sec-Fetch-Site`` in every current
+browser, ``Origin`` on any cross-origin POST in older ones. A request another
+site started is refused here, before any route runs. Mail apps, calendar apps
+and servers send neither header and are not affected (DAV lives outside /api
+anyway).
+"""
+
+from __future__ import annotations
+
+import json
+from urllib.parse import urlsplit
+
+from starlette.datastructures import Headers
+from starlette.types import ASGIApp, Receive, Scope, Send
+
+from app.config import get_settings
+
+_SAFE_METHODS = frozenset({"GET", "HEAD", "OPTIONS"})
+_BODY = json.dumps(
+    {"error": {"code": "cross_site", "message": "request refused: sent from another site"}}
+).encode()
+
+
+def _hostname(value: str) -> str:
+    """``host[:port]`` -> ``host``, lower-cased (IPv6 brackets kept)."""
+    value = value.strip().lower()
+    if value.startswith("["):
+        return value.split("]", 1)[0] + "]"
+    return value.rsplit(":", 1)[0] if value.count(":") == 1 else value
+
+
+def is_cross_site(headers: Headers) -> bool:
+    """Whether a browser reports this request as started by another site."""
+    fetch_site = headers.get("sec-fetch-site")
+    if fetch_site is not None:
+        # "same-origin", "same-site" (our own subdomains), "none" (typed or
+        # bookmarked): all fine. Only another site is refused.
+        return fetch_site.strip().lower() == "cross-site"
+    origin = headers.get("origin")
+    if origin is None:
+        return False  # not a browser, or a same-origin request from an old one
+    if origin.strip().lower() == "null":
+        return True  # sandboxed frame, data: URL, file: page
+    origin_host = (urlsplit(origin.strip()).hostname or "").lower()
+    # Our own domain, whatever a reverse proxy did to the Host header.
+    domain = get_settings().app_domain.lower()
+    if origin_host == domain or origin_host.endswith("." + domain):
+        return False
+    # Otherwise the name the browser used: Host, or the one a reverse proxy saw.
+    ours = {_hostname(headers.get("host", ""))}
+    forwarded = headers.get("x-forwarded-host")
+    if forwarded:
+        ours.add(_hostname(forwarded.split(",")[0]))
+    return origin_host not in ours
+
+
+class CrossSiteGuard:
+    """ASGI middleware: 403 on cross-site POST/PUT/PATCH/DELETE under /api/."""
+
+    def __init__(self, app: ASGIApp) -> None:
+        self.app = app
+
+    async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
+        if (
+            scope["type"] == "http"
+            and scope["method"] not in _SAFE_METHODS
+            and scope["path"].startswith("/api/")
+            and is_cross_site(Headers(scope=scope))
+        ):
+            await send(
+                {
+                    "type": "http.response.start",
+                    "status": 403,
+                    "headers": [
+                        (b"content-type", b"application/json"),
+                        (b"content-length", str(len(_BODY)).encode()),
+                    ],
+                }
+            )
+            await send({"type": "http.response.body", "body": _BODY})
+            return
+        await self.app(scope, receive, send)

backend/app/sync/actions.py

@@ -302,7 +302,8 @@ async def restore_thread_job(ctx: dict[str, Any], thread_id: str) -> None:
 
     Each message returns to ``restore_mailbox_id`` (the folder it was in before it
     was archived/trashed) — e.g. a deleted Sent message goes back to Sent. Messages
-    with no recorded origin fall back to the account's Inbox.
+    with no recorded origin fall back to the account's Inbox. Only messages in
+    Archive, Trash or Spam move: the thread's others (your reply in Sent) stay.
     """
     tid = uuid.UUID(thread_id)
     async with session_scope() as session:
@@ -319,10 +320,13 @@ async def restore_thread_job(ctx: dict[str, Any], thread_id: str) -> None:
             await session.scalars(select(Mailbox).where(Mailbox.account_id.in_(account_ids)))
         )
         path_by_id = {mb.id: mb.path for mb in mailboxes}
+        removal_ids = {mb.id for mb in mailboxes if mb.special_use in _REMOVAL_FOLDERS}
         inbox_by_account = {mb.account_id: mb.id for mb in mailboxes if mb.special_use == "inbox"}
         # (message_id, account_id, source_path, target_id) — resolve the target now.
         plan: list[tuple[uuid.UUID, uuid.UUID, str, uuid.UUID, int]] = []
         for m in messages:
+            if m.mailbox_id not in removal_ids:
+                continue  # never removed: nothing to restore
             target_id = m.restore_mailbox_id
             if target_id is None or target_id not in path_by_id:
                 target_id = inbox_by_account.get(m.account_id)

backend/app/sync/engine.py

@@ -172,9 +172,7 @@ class _BackfillProgress:
         self._mailboxes.add(mailbox_path)
         async with session_scope() as session:
             await session.execute(
-                update(Account)
+                update(Account).where(Account.id == self.account.id).values(backfill_done=self.done)
-                .where(Account.id == self.account.id)
-                .values(backfill_done=self.done)
             )
         await get_event_bus().publish(
             "sync.progress",
@@ -321,16 +319,28 @@ async def bootstrap_and_backfill(account_id: uuid.UUID) -> int:
             dedupe = gmail and mailbox.special_use == "archive"
             if since is not None:  # 3months: single windowed pass
                 count += await backfill_mailbox(
-                    provider, account_obj, mailbox, progress, since=since,
+                    provider,
+                    account_obj,
+                    mailbox,
+                    progress,
+                    since=since,
                     dedupe_account_scope=dedupe,
                 )
             else:  # all: recent window first (usable fast), then the remainder
                 count += await backfill_mailbox(
-                    provider, account_obj, mailbox, progress, since=recent_cutoff,
+                    provider,
+                    account_obj,
+                    mailbox,
+                    progress,
+                    since=recent_cutoff,
                     dedupe_account_scope=dedupe,
                 )
                 count += await backfill_mailbox(
-                    provider, account_obj, mailbox, progress, before=recent_cutoff,
+                    provider,
+                    account_obj,
+                    mailbox,
+                    progress,
+                    before=recent_cutoff,
                     dedupe_account_scope=dedupe,
                 )
         await _set_state(account_id, "live")
@@ -491,9 +501,7 @@ async def apply_delta(
         await _reconcile_drafts(provider, account, mailbox)
 
 
-async def _reconcile_drafts(
+async def _reconcile_drafts(provider: ImapSmtpProvider, account: Account, mailbox: Mailbox) -> None:
-    provider: ImapSmtpProvider, account: Account, mailbox: Mailbox
-) -> None:
     """Drop DB rows for drafts that no longer exist on the server (were expunged)."""
     from app.db import session_scope
 
@@ -548,13 +556,13 @@ async def live_loop(
         await provider.verify()  # signed in: the account is reachable
         if health is not None:
             await health.ok()
+        first = True
         while not stop.is_set():
-            try:
+            # Catch up before each IDLE, not only after it: IDLE reports what
-                await provider.idle(mailbox_path)
+            # arrives from now on, so mail that came while this loop was not
-            except ProviderNotSupported:
+            # running (a new account's first minutes, a reconnect, a worker
-                await asyncio.sleep(idle_fallback)
+            # restart) would otherwise wait for the next new message or the
-            if stop.is_set():
+            # IDLE timeout (10 min) to show.
-                break
             async with session_scope() as session:
                 mailbox = await session.scalar(
                     select(Mailbox).where(
@@ -562,14 +570,23 @@ async def live_loop(
                     )
                 )
                 mailbox_obj = mailbox
-            if mailbox_obj is None:
+            if mailbox_obj is not None:
+                delta = await provider.poll(
+                    mailbox_path,
+                    last_seen_uid=mailbox_obj.last_seen_uid,
+                    highestmodseq=mailbox_obj.highestmodseq,
+                )
+                await apply_delta(provider, account_obj, mailbox_obj, delta)
+            elif not first:
+                break  # the folder is gone
+            # else: the account's first sync has not recorded the folder yet.
+            first = False
+            if stop.is_set():
                 break
-            delta = await provider.poll(
+            try:
-                mailbox_path,
+                await provider.idle(mailbox_path)
-                last_seen_uid=mailbox_obj.last_seen_uid,
+            except ProviderNotSupported:
-                highestmodseq=mailbox_obj.highestmodseq,
+                await asyncio.sleep(idle_fallback)
-            )
-            await apply_delta(provider, account_obj, mailbox_obj, delta)
     finally:
         await provider.close()
 
@@ -630,9 +647,7 @@ async def poll_folders_once(
         await provider.close()
 
 
-async def _poll_secondary_once(
+async def _poll_secondary_once(account_id: uuid.UUID, health: AccountHealth | None = None) -> None:
-    account_id: uuid.UUID, health: AccountHealth | None = None
-) -> None:
     await poll_folders_once(account_id, include_inbox=False, health=health)
 
 

backend/app/sync/folder_names.py

@@ -28,24 +28,52 @@ def _compact(name: str) -> str:
 # Localized folder names by special_use. Written readably; compacted at load.
 _NAMES: dict[str, list[str]] = {
     "sent": [
-        "sent", "sent items", "sent mail", "sent messages",  # English / Outlook / Gmail
+        "sent",
-        "wysłane", "elementy wysłane", "wiadomości wysłane",  # Polish
+        "sent items",
-        "gesendet", "gesendete objekte", "gesendete elemente",  # German
+        "sent mail",
-        "envoyés", "éléments envoyés", "messages envoyés", "courrier envoyé",  # French
+        "sent messages",  # English / Outlook / Gmail
-        "enviados", "elementos enviados", "correo enviado",  # Spanish
+        "wysłane",
-        "inviata", "posta inviata", "messaggi inviati",  # Italian
+        "elementy wysłane",
-        "verzonden", "verzonden items", "verzonden berichten",  # Dutch
+        "wiadomości wysłane",  # Polish
-        "enviadas", "itens enviados", "mensagens enviadas",  # Portuguese
+        "gesendet",
-        "отправленные", "исходящие",  # Russian
+        "gesendete objekte",
-        "skickat", "skickade", "skickade objekt",  # Swedish
+        "gesendete elemente",  # German
-        "sendt", "sendte", "sendte elementer",  # Norwegian / Danish
+        "envoyés",
+        "éléments envoyés",
+        "messages envoyés",
+        "courrier envoyé",  # French
+        "enviados",
+        "elementos enviados",
+        "correo enviado",  # Spanish
+        "inviata",
+        "posta inviata",
+        "messaggi inviati",  # Italian
+        "verzonden",
+        "verzonden items",
+        "verzonden berichten",  # Dutch
+        "enviadas",
+        "itens enviados",
+        "mensagens enviadas",  # Portuguese
+        "отправленные",
+        "исходящие",  # Russian
+        "skickat",
+        "skickade",
+        "skickade objekt",  # Swedish
+        "sendt",
+        "sendte",
+        "sendte elementer",  # Norwegian / Danish
         "lähetetyt",  # Finnish
-        "odeslané", "odeslaná pošta",  # Czech
+        "odeslané",
+        "odeslaná pošta",  # Czech
     ],
     "drafts": [
-        "drafts", "draft",
+        "drafts",
-        "robocze", "kopie robocze", "wersje robocze",
+        "draft",
-        "entwürfe", "entwurf",
+        "robocze",
+        "kopie robocze",
+        "wersje robocze",
+        "entwürfe",
+        "entwurf",
         "brouillons",
         "borradores",
         "bozze",
@@ -58,44 +86,80 @@ _NAMES: dict[str, list[str]] = {
         "koncepty",  # Czech
     ],
     "trash": [
-        "trash", "deleted", "deleted items", "deleted messages", "bin", "recycle bin",
+        "trash",
+        "deleted",
+        "deleted items",
+        "deleted messages",
+        "bin",
+        "recycle bin",
         "kosz",
-        "papierkorb", "gelöschte objekte", "gelöschte elemente",
+        "papierkorb",
-        "corbeille", "éléments supprimés",
+        "gelöschte objekte",
-        "papelera", "elementos eliminados",
+        "gelöschte elemente",
-        "cestino", "posta eliminata",
+        "corbeille",
-        "prullenbak", "verwijderde items",
+        "éléments supprimés",
-        "lixeira", "lixo", "itens excluídos",
+        "papelera",
-        "корзина", "удаленные",
+        "elementos eliminados",
-        "papperskorg", "borttaget",
+        "cestino",
-        "papirkurv", "slettet",
+        "posta eliminata",
-        "roskakori", "poistetut",
+        "prullenbak",
+        "verwijderde items",
+        "lixeira",
+        "lixo",
+        "itens excluídos",
+        "корзина",
+        "удаленные",
+        "papperskorg",
+        "borttaget",
+        "papirkurv",
+        "slettet",
+        "roskakori",
+        "poistetut",
         "koš",  # Czech
     ],
     "junk": [
-        "junk", "junk email", "junk e-mail", "spam", "bulk mail", "bulk",
+        "junk",
-        "wiadomości-śmieci", "niechciane",
+        "junk email",
-        "unerwünscht", "werbung",
+        "junk e-mail",
-        "courrier indésirable", "indésirables", "pourriel",
+        "spam",
-        "correo no deseado", "no deseado", "correo basura",
+        "bulk mail",
-        "posta indesiderata", "indesiderata",
+        "bulk",
-        "ongewenst", "ongewenste e-mail",
+        "wiadomości-śmieci",
+        "niechciane",
+        "unerwünscht",
+        "werbung",
+        "courrier indésirable",
+        "indésirables",
+        "pourriel",
+        "correo no deseado",
+        "no deseado",
+        "correo basura",
+        "posta indesiderata",
+        "indesiderata",
+        "ongewenst",
+        "ongewenste e-mail",
         "lixo eletrônico",
-        "спам", "нежелательная почта",
+        "спам",
-        "skräp", "skräppost",
+        "нежелательная почта",
+        "skräp",
+        "skräppost",
         "uønsket",
         "roskaposti",
         "nevyžádaná pošta",
     ],
     "archive": [
-        "archive", "archives", "all mail",
+        "archive",
+        "archives",
+        "all mail",
         "archiwum",
         "archiv",
         "archivio",
         "archivo",
         "archief",
-        "arquivo", "arquivo morto",
+        "arquivo",
-        "архив", "вся почта",
+        "arquivo morto",
+        "архив",
+        "вся почта",
         "arkiv",
         "arkisto",
     ],

backend/app/sync/provider_factory.py

@@ -33,5 +33,6 @@ def build_provider(account: Account) -> ImapSmtpProvider:
         smtp_tls=str(smtp.get("tls", "ssl")),
         username=account.email,
         password=password,
+        public_only=True,  # a server the user named: never one inside our network
     )
     return ImapSmtpProvider(config)

backend/app/ws.py

@@ -18,6 +18,7 @@ from app.events import get_event_bus
 from app.identity.cookies import SESSION_COOKIE_INSECURE, SESSION_COOKIE_SECURE
 from app.identity.sessions import resolve_session
 from app.redis_client import get_redis
+from app.security.cross_site import is_cross_site
 from app.sync import leases
 
 logger = logging.getLogger(__name__)
@@ -27,6 +28,12 @@ router = APIRouter()
 
 @router.websocket("/ws")
 async def ws_endpoint(websocket: WebSocket) -> None:
+    # Only our own pages may listen in: a socket another site opens is refused
+    # even if the browser sent the session cookie with it (cross-site WebSocket
+    # hijacking; SameSite=Lax already stops current browsers from sending it).
+    if is_cross_site(websocket.headers):
+        await websocket.close(code=1008)
+        return
     token = websocket.cookies.get(SESSION_COOKIE_SECURE) or websocket.cookies.get(
         SESSION_COOKIE_INSECURE, ""
     )

backend/scripts/backfill_delivery_id.py

@@ -16,9 +16,7 @@ from app.models import Message
 
 async def main() -> None:
     async with session_scope() as session:
-        rows = list(
+        rows = list(await session.scalars(select(Message).where(Message.delivery_id.is_(None))))
-            await session.scalars(select(Message).where(Message.delivery_id.is_(None)))
-        )
         fixed = 0
         for m in rows:
             try:

backend/scripts/reindex_address_parts.py

@@ -42,9 +42,7 @@ async def main() -> None:
                 update(Message)
                 .where(Message.id == msg.id)
                 .values(
-                    body_indexed=Message.body_indexed.op("||")(
+                    body_indexed=Message.body_indexed.op("||")(func.to_tsvector(_TS_CONFIG, blob))
-                        func.to_tsvector(_TS_CONFIG, blob)
-                    )
                 )
             )
             updated += 1

backend/tests/accounts/test_discovery.py

@@ -37,10 +37,14 @@ AUTOCONFIG_XML = """<?xml version="1.0"?>
 def _skip_ssrf(monkeypatch) -> None:  # type: ignore[no-untyped-def]
     """Bypass the real DNS/public-IP check so respx can intercept the fetch."""
 
-    async def ok(_host: str) -> None:
+    async def ok(_host: str) -> list[str]:
-        return None
+        return ["93.184.216.34"]
+
+    async def unpinned(url: str) -> tuple[str, dict[str, str], dict[str, str]]:
+        return url, {}, {}  # respx matches on the host name, not the pinned IP
 
     monkeypatch.setattr(ssrf, "assert_host_is_public", ok)
+    monkeypatch.setattr(ssrf, "_pinned", unpinned)
 
 
 # --- XML parsing -------------------------------------------------------------

backend/tests/api/test_api.py

@@ -310,7 +310,8 @@ async def test_attachment_download_non_ascii_filename(api: ApiCtx) -> None:
     await api.session.commit()
 
     aid = next(
-        a["id"] for a in (await api.client.get(f"/api/messages/{mid}/attachments")).json()
+        a["id"]
+        for a in (await api.client.get(f"/api/messages/{mid}/attachments")).json()
         if a["filename"] == name
     )
     resp = await api.client.get(f"/api/messages/{mid}/attachments/{aid}")
@@ -404,8 +405,11 @@ async def test_folder_counts(api: ApiCtx) -> None:
 async def test_thread_collapses_cross_account_duplicate(api: ApiCtx) -> None:
     assert api.session is not None
     # The kickoff thread's first message; give it a real delivery_id.
-    kickoff = next(t for t in (await api.client.get("/api/threads")).json()["threads"]
+    kickoff = next(
-                   if t["message_count"] == 2)
+        t
+        for t in (await api.client.get("/api/threads")).json()["threads"]
+        if t["message_count"] == 2
+    )
     detail = (await api.client.get(f"/api/threads/{kickoff['id']}")).json()
     first_id = uuid.UUID(detail["messages"][0]["id"])
     first = await api.session.get(Message, first_id)
@@ -414,20 +418,32 @@ async def test_thread_collapses_cross_account_duplicate(api: ApiCtx) -> None:
 
     # A second account receives the SAME email (same delivery_id) into the same thread.
     acct2 = Account(
-        user_id=api.user_id, email="me2@example.com", imap_config={}, smtp_config={},
+        user_id=api.user_id,
-        secret_ct=b"", discovery_src="manual",
+        email="me2@example.com",
+        imap_config={},
+        smtp_config={},
+        secret_ct=b"",
+        discovery_src="manual",
     )
     api.session.add(acct2)
     await api.session.flush()
     inbox2 = Mailbox(account_id=acct2.id, user_id=api.user_id, path="INBOX", special_use="inbox")
     api.session.add(inbox2)
     await api.session.flush()
-    api.session.add(Message(
+    api.session.add(
-        user_id=api.user_id, account_id=acct2.id, mailbox_id=inbox2.id, uid=1,
+        Message(
-        thread_id=first.thread_id, message_id_hdr="<synthetic@synthetic.local>",
+            user_id=api.user_id,
-        delivery_id="<shared@x.com>", subject=first.subject,
+            account_id=acct2.id,
-        internal_date=datetime.now(UTC), blob_sha256="z" * 64,  # later -> first stays the rep
+            mailbox_id=inbox2.id,
-    ))
+            uid=1,
+            thread_id=first.thread_id,
+            message_id_hdr="<synthetic@synthetic.local>",
+            delivery_id="<shared@x.com>",
+            subject=first.subject,
+            internal_date=datetime.now(UTC),
+            blob_sha256="z" * 64,  # later -> first stays the rep
+        )
+    )
     await api.session.commit()
 
     body = (await api.client.get(f"/api/threads/{kickoff['id']}")).json()

backend/tests/api/test_saved_searches.py

@@ -104,9 +104,7 @@ async def test_saved_search_crud_and_upsert(ctx: Ctx) -> None:
 
 async def test_saved_search_requires_csrf(ctx: Ctx) -> None:
     # No CSRF header -> rejected (state-changing route).
-    resp = await ctx.client.post(
+    resp = await ctx.client.post("/api/saved-searches", json={"name": "x", "query": "y"})
-        "/api/saved-searches", json={"name": "x", "query": "y"}
-    )
     assert resp.status_code == 403
 
 

backend/tests/conftest.py

@@ -21,6 +21,8 @@ os.environ.setdefault("BLOB_ROOT", "./var/blobs-test")
 # Hosted mailboxes off: tests that need the mail server turn them on themselves
 # (tests/hosted/), against the dev stack's Stalwart container.
 os.environ["HOSTED_MAILBOXES"] = "false"
+# No calls to the breached-password service from tests (app/identity/password_policy.py).
+os.environ["PASSWORD_BREACH_CHECK"] = "false"
 for _key, _value in {
     "STALWART_URL": "http://127.0.0.1:8180",
     "STALWART_ADMIN_SECRET": "stalwart_admin_dev",

backend/tests/mail/test_actions.py

@@ -421,3 +421,36 @@ async def test_delete_keeps_rows_while_unreachable(ctx: Ctx, monkeypatch) -> Non
             select(func.count()).select_from(Message).where(Message.thread_id == ctx.thread_id)
         )
         assert left == len(ctx.message_ids)  # kept: the server still has them
+
+
+async def test_restore_moves_only_what_was_removed(ctx: Ctx, monkeypatch) -> None:  # type: ignore[no-untyped-def]
+    """A thread restored from Spam brings its spam back; the user's own reply in
+    Sent (never removed, so no recorded origin) stays in Sent."""
+    sent = Mailbox(account_id=None, user_id=ctx.user_id, path="Sent", special_use="sent")
+    first = await ctx.session.get(Message, ctx.message_ids[0])
+    reply = await ctx.session.get(Message, ctx.message_ids[1])
+    assert first is not None and reply is not None
+    sent.account_id = first.account_id
+    ctx.session.add(sent)
+    await ctx.session.flush()
+    first.mailbox_id = ctx.archive_id  # removed, origin unknown (as when synced in)
+    reply.mailbox_id = sent.id
+    await ctx.session.commit()
+
+    moves: list[tuple[int, str, str]] = []
+
+    class Recorder:
+        async def move(self, uid: int, src: str, dst: str) -> int:
+            moves.append((uid, src, dst))
+            return 100 + uid
+
+        async def close(self) -> None:
+            return None
+
+    monkeypatch.setattr(sync_actions, "build_provider", lambda _a: Recorder())
+    await sync_actions.restore_thread_job({"job_try": 1}, str(ctx.thread_id))
+    assert moves == [(first.uid, "Archive", "INBOX")]
+    ctx.session.expunge_all()
+    async with session_scope() as verify:
+        kept = await verify.get(Message, ctx.message_ids[1])
+        assert kept is not None and kept.mailbox_id == sent.id

backend/tests/plugins/test_calendar_reminders.py

@@ -104,7 +104,8 @@ async def test_due_reminders_are_sent_once(ctx) -> None:  # type: ignore[no-unty
     assert await run(MON_9 - timedelta(minutes=60)) == 1  # the 1-hour reminder
     assert sent[-1]["title"] == "Dentist"
     assert sent[-1]["body"] == "In 1 hour, 09:00 · Main St 4"
-    assert sent[-1]["url"].startswith("/p/calendar?date=2031-06-02&event=") and sent[-1]["sticky"] is True
+    assert sent[-1]["url"].startswith("/p/calendar?date=2031-06-02&event=")
+    assert sent[-1]["sticky"] is True
     assert await run(MON_9 - timedelta(minutes=59)) == 0  # not again
     # The worker was down when the 10-minute reminder came due: sent late, once.
     assert await run(MON_9 - timedelta(minutes=4)) == 1

backend/tests/plugins/test_filters_plugin.py

@@ -49,8 +49,12 @@ async def ctx() -> AsyncIterator[_Ctx]:
         s.add(user)
         await s.flush()
         account = Account(
-            user_id=user.id, email="me@example.com", imap_config={}, smtp_config={},
+            user_id=user.id,
-            secret_ct=b"", discovery_src="manual",
+            email="me@example.com",
+            imap_config={},
+            smtp_config={},
+            secret_ct=b"",
+            discovery_src="manual",
         )
         s.add(account)
         await s.flush()
@@ -64,12 +68,17 @@ async def ctx() -> AsyncIterator[_Ctx]:
         s.add(thread)
         await s.flush()
         msg = Message(
-            user_id=user.id, account_id=account.id, mailbox_id=mbox.id, uid=1,
+            user_id=user.id,
+            account_id=account.id,
+            mailbox_id=mbox.id,
+            uid=1,
             thread_id=thread.id,
             subject="Your Invoice 123",
             from_addr=[{"name": "Billing", "email": "billing@acme.com"}],
             to_addr=[{"name": "Me", "email": "me@example.com"}],
-            flags=[], internal_date=datetime.now(UTC), blob_sha256="",
+            flags=[],
+            internal_date=datetime.now(UTC),
+            blob_sha256="",
         )
         s.add(msg)
         await s.commit()
@@ -99,24 +108,30 @@ async def _flags(ctx: _Ctx) -> list[str]:
 
 
 async def test_hook_applies_flag_on_match(ctx: _Ctx) -> None:
-    await sdk("filters").kv(ctx.user_id).set(
+    await (
-        "_rules", [{"field": "subject", "contains": "invoice", "action": "read"}]
+        sdk("filters")
+        .kv(ctx.user_id)
+        .set("_rules", [{"field": "subject", "contains": "invoice", "action": "read"}])
     )
     await on_message_new({"user_id": str(ctx.user_id), "message_id": str(ctx.message_id)})
     assert "\\Seen" in await _flags(ctx)
 
 
 async def test_hook_no_match_leaves_flags(ctx: _Ctx) -> None:
-    await sdk("filters").kv(ctx.user_id).set(
+    await (
-        "_rules", [{"field": "from", "contains": "newsletter@somewhere", "action": "pin"}]
+        sdk("filters")
+        .kv(ctx.user_id)
+        .set("_rules", [{"field": "from", "contains": "newsletter@somewhere", "action": "pin"}])
     )
     await on_message_new({"user_id": str(ctx.user_id), "message_id": str(ctx.message_id)})
     assert await _flags(ctx) == []
 
 
 async def test_hook_pin_applies_flagged(ctx: _Ctx) -> None:
-    await sdk("filters").kv(ctx.user_id).set(
+    await (
-        "_rules", [{"field": "from", "contains": "billing@acme", "action": "pin"}]
+        sdk("filters")
+        .kv(ctx.user_id)
+        .set("_rules", [{"field": "from", "contains": "billing@acme", "action": "pin"}])
     )
     await on_message_new({"user_id": str(ctx.user_id), "message_id": str(ctx.message_id)})
     assert "\\Flagged" in await _flags(ctx)  # "pin" == the \Flagged flag in this app
@@ -124,16 +139,16 @@ async def test_hook_pin_applies_flagged(ctx: _Ctx) -> None:
 
 async def test_hook_matches_on_to(ctx: _Ctx) -> None:
     # Multi-account setups match on the recipient address.
-    await sdk("filters").kv(ctx.user_id).set(
+    await (
-        "_rules", [{"field": "to", "contains": "me@example.com", "action": "read"}]
+        sdk("filters")
+        .kv(ctx.user_id)
+        .set("_rules", [{"field": "to", "contains": "me@example.com", "action": "read"}])
     )
     await on_message_new({"user_id": str(ctx.user_id), "message_id": str(ctx.message_id)})
     assert "\\Seen" in await _flags(ctx)
 
 
-async def test_hook_trash_moves_thread_to_trash(
+async def test_hook_trash_moves_thread_to_trash(ctx: _Ctx, monkeypatch: pytest.MonkeyPatch) -> None:
-    ctx: _Ctx, monkeypatch: pytest.MonkeyPatch
-) -> None:
     calls: list[tuple[object, ...]] = []
 
     async def fake_enqueue(name: str, *args: object, **kwargs: object) -> None:
@@ -141,8 +156,10 @@ async def test_hook_trash_moves_thread_to_trash(
 
     # trash() enqueues the same job the UI Delete uses (imported from app.queue).
     monkeypatch.setattr("app.queue.enqueue_job", fake_enqueue)
-    await sdk("filters").kv(ctx.user_id).set(
+    await (
-        "_rules", [{"field": "subject", "contains": "invoice", "action": "trash"}]
+        sdk("filters")
+        .kv(ctx.user_id)
+        .set("_rules", [{"field": "subject", "contains": "invoice", "action": "trash"}])
     )
     await on_message_new({"user_id": str(ctx.user_id), "message_id": str(ctx.message_id)})
     assert ("move_thread_to_folder_job", str(ctx.thread_id), "trash") in calls

backend/tests/plugins/test_hello_plugin.py

@@ -68,9 +68,7 @@ async def ctx() -> AsyncIterator[_Ctx]:
         await c.client_a.aclose()
         await c.client_b.aclose()
         async with sm() as s:
-            await s.execute(
+            await s.execute(delete(User).where(User.id.in_([c.user_a, c.user_b])))
-                delete(User).where(User.id.in_([c.user_a, c.user_b]))
-            )
             await s.execute(
                 text("DELETE FROM plg_hello_note WHERE user_id IN (:a, :b)"),
                 {"a": str(c.user_a), "b": str(c.user_b)},

backend/tests/plugins/test_migrate.py

@@ -51,9 +51,10 @@ async def test_install_run_uninstall_dropdata_roundtrip() -> None:
 
         # Table exists, RLS is enabled on it, and the per-plugin version table is present.
         assert await _regclass("plg_demo_note") == "plg_demo_note"
-        assert await _scalar(
+        assert (
-            "SELECT relrowsecurity FROM pg_class WHERE relname = 'plg_demo_note'"
+            await _scalar("SELECT relrowsecurity FROM pg_class WHERE relname = 'plg_demo_note'")
-        ) is True
+            is True
+        )
         assert await _regclass("alembic_version_plg_demo") == "alembic_version_plg_demo"
 
         # --drop-data removes the table AND the version table: zero residue.

backend/tests/plugins/test_sdk_messages.py

@@ -27,8 +27,12 @@ async def test_messages_header_reads_raw_header() -> None:
         s.add(user)
         await s.flush()
         account = Account(
-            user_id=user.id, email="me@example.com", imap_config={}, smtp_config={},
+            user_id=user.id,
-            secret_ct=b"", discovery_src="manual",
+            email="me@example.com",
+            imap_config={},
+            smtp_config={},
+            secret_ct=b"",
+            discovery_src="manual",
         )
         s.add(account)
         await s.flush()
@@ -44,8 +48,14 @@ async def test_messages_header_reads_raw_header() -> None:
         sha = blobstore.store(user.id, raw.as_bytes())
 
         msg = Message(
-            user_id=user.id, account_id=account.id, mailbox_id=mbox.id, uid=1,
+            user_id=user.id,
-            subject="Weekly digest", flags=[], internal_date=datetime.now(UTC), blob_sha256=sha,
+            account_id=account.id,
+            mailbox_id=mbox.id,
+            uid=1,
+            subject="Weekly digest",
+            flags=[],
+            internal_date=datetime.now(UTC),
+            blob_sha256=sha,
         )
         s.add(msg)
         await s.commit()

backend/tests/plugins/test_ui_manifest_api.py

@@ -44,9 +44,7 @@ async def test_ui_manifest_endpoint() -> None:
     )
     try:
         # Unauthenticated request is rejected.
-        async with httpx.AsyncClient(
+        async with httpx.AsyncClient(transport=transport, base_url="http://testserver") as anon:
-            transport=transport, base_url="http://testserver"
-        ) as anon:
             assert (await anon.get("/api/plugins/ui-manifest")).status_code == 401
 
         resp = await client.get("/api/plugins/ui-manifest")

backend/tests/providers/test_parsing.py

@@ -100,7 +100,15 @@ def test_parse_search_uids() -> None:
 
 def test_parse_vanished() -> None:
     # aioimaplib strips the leading "* " before buffering the line.
-    assert parse_vanished([b"VANISHED (EARLIER) 300:305,405"]) == [300, 301, 302, 303, 304, 305, 405]  # noqa: E501
+    assert parse_vanished([b"VANISHED (EARLIER) 300:305,405"]) == [
+        300,
+        301,
+        302,
+        303,
+        304,
+        305,
+        405,
+    ]  # noqa: E501
     # Live-expunge form (no EARLIER) and a descending range are both handled.
     assert parse_vanished([b"VANISHED 41", b"VANISHED (EARLIER) 5:3"]) == [41, 3, 4, 5]
     # Non-VANISHED lines are ignored; non-bytes entries are skipped.

backend/tests/search/test_meili.py

@@ -52,9 +52,7 @@ async def test_meili_typo_tolerance_and_filters() -> None:
         await backend.index(_doc(user_id))
 
         # Acceptance (§12 M2): a typo still finds the message.
-        hits, _c = await backend.query(
+        hits, _c = await backend.query(to_search_query("invocie", user_id), limit=10, cursor=None)
-            to_search_query("invocie", user_id), limit=10, cursor=None
-        )
         if not hits:  # wait for the async index task
             assert await _poll(backend, "invocie", user_id) == 1
             hits, _c = await backend.query(

backend/tests/search/test_search_api.py

@@ -159,8 +159,12 @@ async def test_search_excludes_trash_by_default(ctx: Ctx) -> None:
     ctx.session.add(trash)
     await ctx.session.flush()
     await _ingest(
-        ctx, frm="X <x@corp.com>", subject="zephyr in trash", body="bye",
+        ctx,
-        mailbox_id=trash.id, special="trash",
+        frm="X <x@corp.com>",
+        subject="zephyr in trash",
+        body="bye",
+        mailbox_id=trash.id,
+        special="trash",
     )
     assert await _search(ctx, "zephyr") == 1  # inbox only; the trashed one is hidden
     assert await _search(ctx, "in:trash zephyr") == 1  # explicit -> searches Trash

backend/tests/security/test_hardening.py

@@ -0,0 +1,285 @@
+"""Fixes from the 2026-10-14 security assessment (ultimo-security-report.md):
+cross-site requests refused (login CSRF), terse validation errors, the new-password
+policy, link schemes in message HTML, and DNS-rebinding-proof outbound fetches."""
+
+from __future__ import annotations
+
+import asyncio
+import uuid
+from collections.abc import AsyncIterator
+
+import httpx
+import pytest
+import pytest_asyncio
+from httpx import ASGITransport
+from starlette.datastructures import Headers
+
+from app.accounts import ssrf
+from app.config import get_settings
+from app.identity import password_policy
+from app.identity.password_policy import PasswordRejected, check_new_password
+from app.indexer.sanitize import sanitize_html
+from app.main import create_app
+from app.security.cross_site import is_cross_site
+
+
+@pytest_asyncio.fixture
+async def client() -> AsyncIterator[httpx.AsyncClient]:
+    async with httpx.AsyncClient(
+        transport=ASGITransport(app=create_app()), base_url="http://mail.example.org"
+    ) as c:
+        yield c
+
+
+def _login(client: httpx.AsyncClient, headers: dict[str, str]):  # type: ignore[no-untyped-def]
+    return client.post(
+        "/api/auth/login", json={"handle": "nobody", "password": "x"}, headers=headers
+    )
+
+
+# --- cross-site requests (finding 3) --------------------------------------------------
+
+
+@pytest.mark.parametrize(
+    "headers",
+    [
+        {"Sec-Fetch-Site": "cross-site", "Origin": "https://evil.example"},
+        {"Origin": "https://evil.example"},  # an older browser: Origin only
+        {"Origin": "null"},  # a sandboxed frame
+    ],
+)
+async def test_sign_in_from_another_site_is_refused(
+    client: httpx.AsyncClient, headers: dict[str, str]
+) -> None:
+    resp = await _login(client, headers)
+    assert resp.status_code == 403
+    assert resp.json()["error"]["code"] == "cross_site"
+
+
+@pytest.mark.parametrize(
+    "headers",
+    [
+        {"Sec-Fetch-Site": "same-origin", "Origin": "http://mail.example.org"},
+        {"Origin": "http://mail.example.org"},
+        {"Origin": "https://mail.example.org:8443"},  # the port does not matter
+        {"Sec-Fetch-Site": "same-site"},  # our own subdomain
+        {"Sec-Fetch-Site": "none"},  # typed into the address bar
+        {},  # not a browser (scripts, mail apps)
+    ],
+)
+async def test_sign_in_from_our_own_pages_goes_through(
+    client: httpx.AsyncClient, headers: dict[str, str]
+) -> None:
+    resp = await _login(client, headers)
+    assert resp.status_code == 401  # evaluated: wrong credentials, not refused
+    assert resp.json()["error"]["code"] == "invalid_credentials"
+
+
+async def test_reads_from_another_site_are_not_refused(client: httpx.AsyncClient) -> None:
+    resp = await client.get("/api/auth/registration", headers={"Sec-Fetch-Site": "cross-site"})
+    assert resp.status_code == 200
+
+
+def test_origin_on_our_own_domain_passes_whatever_the_host_header() -> None:
+    domain = get_settings().app_domain
+    headers = Headers({"origin": f"https://{domain}", "host": "localhost:8088"})
+    assert is_cross_site(headers) is False
+    sub = Headers({"origin": f"https://mail.{domain}", "host": "localhost:8088"})
+    assert is_cross_site(sub) is False
+    lookalike = Headers({"origin": f"https://evil{domain}", "host": "localhost:8088"})
+    assert is_cross_site(lookalike) is True
+
+
+def test_origin_matches_the_name_a_reverse_proxy_saw() -> None:
+    headers = Headers(
+        {"origin": "https://ultimo.email", "host": "web:80", "x-forwarded-host": "ultimo.email"}
+    )
+    assert is_cross_site(headers) is False
+
+
+# --- validation errors (finding 5) ----------------------------------------------------
+
+
+async def test_validation_errors_do_not_spell_out_the_request_model(
+    client: httpx.AsyncClient,
+) -> None:
+    resp = await client.post("/api/auth/login", json={})
+    assert resp.status_code == 422
+    body = resp.json()
+    assert "detail" not in body
+    assert body["error"]["code"] == "validation_error"
+    assert body["error"]["message"].startswith("handle:")
+
+
+async def test_a_too_short_password_says_so(client: httpx.AsyncClient) -> None:
+    resp = await client.post("/api/auth/register", json={"localpart": "abcde", "password": "123"})
+    assert resp.status_code == 422
+    assert "password" in resp.json()["error"]["message"]
+
+
+async def test_new_passwords_are_capped_at_128(client: httpx.AsyncClient) -> None:
+    resp = await client.post(
+        "/api/auth/register", json={"localpart": "abcde", "password": "x" * 129}
+    )
+    assert resp.status_code == 422
+
+
+# --- new-password policy (finding 6) --------------------------------------------------
+
+
+@pytest.mark.parametrize(
+    "password",
+    ["password123", "Password123", "12345678", "aaaaaaaaaa", "abababab", "jsmith2026"],
+)
+async def test_guessable_passwords_are_refused(password: str) -> None:
+    with pytest.raises(PasswordRejected):
+        await check_new_password(password, "jsmith@example.org")
+
+
+async def test_a_decent_password_passes() -> None:
+    await check_new_password("correct horse battery", "jsmith@example.org")
+
+
+async def test_breached_passwords_are_refused(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(get_settings(), "password_breach_check", True)
+    sha = "A" * 40
+
+    async def breached(_password: str) -> bool:
+        return True
+
+    monkeypatch.setattr(password_policy, "_breached", breached)
+    with pytest.raises(PasswordRejected) as err:
+        await check_new_password("long unusual phrase " + sha, "jsmith@example.org")
+    assert err.value.code == "breached_password"
+
+
+async def test_the_breach_service_being_down_does_not_block_sign_up(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    def unreachable(request: httpx.Request) -> httpx.Response:
+        raise httpx.ConnectError("down", request=request)
+
+    real_client = httpx.AsyncClient
+
+    def client_factory(*args, **kwargs):  # type: ignore[no-untyped-def]
+        return real_client(transport=httpx.MockTransport(unreachable))
+
+    monkeypatch.setattr(password_policy.httpx, "AsyncClient", client_factory)
+    assert await password_policy._breached("anything at all") is False
+
+
+async def test_sign_up_with_a_common_password_is_refused(client: httpx.AsyncClient) -> None:
+    resp = await client.post(
+        "/api/auth/register",
+        json={"localpart": f"pw{uuid.uuid4().hex[:8]}", "password": "password123"},
+    )
+    assert resp.status_code == 400
+    assert resp.json()["error"]["code"] == "weak_password"
+
+
+# --- message HTML (V2) ----------------------------------------------------------------
+
+
+@pytest.mark.parametrize(
+    "html",
+    [
+        '<a href="data:text/html,<script>alert(1)</script>">x</a>',
+        '<a href="javascript:alert(1)">x</a>',
+        '<a href="jav&#x09;ascript:alert(1)">x</a>',
+        '<a href="cid:part1">x</a>',
+        "<img src=x onerror=alert(1)>",
+        "<svg onload=alert(1)><circle/></svg>",
+        "<math><mtext><table><mglyph><style><img src=x onerror=alert(1)>",
+        '<noscript><p title="</noscript><img src=x onerror=alert(1)>">',
+        '<iframe srcdoc="<script>alert(1)</script>"></iframe>',
+        '<div style="width:expression(alert(1))">x</div>',
+        '<meta http-equiv="refresh" content="0;url=https://evil.example">',
+        '<base href="https://evil.example/">',
+        '<form action="https://evil.example"><input type=password></form>',
+    ],
+)
+def test_no_active_content_survives(html: str) -> None:
+    out = sanitize_html(html, uuid.uuid4()).html.lower()
+    for marker in (
+        "<script", "onerror", "onload", "javascript:", "data:text", "cid:", "expression(",
+        "<iframe", "<meta", "<base", "<form", "<svg", "<math",
+    ):  # fmt: skip
+        assert marker not in out, (html, out)
+
+
+def test_ordinary_links_stay() -> None:
+    out = sanitize_html(
+        '<a href="https://example.com/x">w</a><a href="mailto:a@b.c">m</a>', uuid.uuid4()
+    ).html
+    assert 'href="https://example.com/x"' in out and 'href="mailto:a@b.c"' in out
+
+
+async def test_the_message_document_carries_its_own_strict_policy() -> None:
+    from app.api import messages
+
+    resp = messages._html("<p>x</p>")
+    csp = resp.headers["content-security-policy"]
+    assert "script-src 'none'" in csp and "sandbox" in csp
+
+
+# --- outbound fetches (V3) ------------------------------------------------------------
+
+
+@pytest.mark.parametrize(
+    "ip", ["100.64.0.1", "::ffff:127.0.0.1", "fd00::1", "169.254.169.254", "fe80::1%eth0"]
+)
+def test_more_non_public_addresses_are_recognised(ip: str) -> None:
+    assert ssrf._is_public_ip(ip) is False
+
+
+async def test_requests_go_to_the_address_that_was_checked(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    answers = iter([["93.184.216.34"], ["127.0.0.1"]])  # a rebinding DNS server
+
+    async def resolve(_host: str) -> list[str]:
+        return next(answers)
+
+    monkeypatch.setattr(ssrf, "_resolve_all", resolve)
+    url, headers, extensions = await ssrf._pinned("https://cal.example.com:8443/dav/?a=1")
+    assert url == "https://93.184.216.34:8443/dav/?a=1"
+    assert headers == {"Host": "cal.example.com:8443"}
+    assert extensions == {"sni_hostname": "cal.example.com"}
+
+
+async def test_pinning_prefers_ipv4(monkeypatch: pytest.MonkeyPatch) -> None:
+    async def resolve(_host: str) -> list[str]:
+        return ["2606:4700::6810:84e5", "104.16.132.229"]
+
+    monkeypatch.setattr(ssrf, "_resolve_all", resolve)
+    url, _, _ = await ssrf._pinned("https://example.com/")
+    assert url == "https://104.16.132.229/"
+
+
+async def test_mail_servers_are_checked_again_at_every_connection(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    from app.providers.base import ProviderConnectError
+    from app.providers.imap_smtp import ImapSmtpProvider, ProviderConfig
+
+    async def resolve(_host: str) -> list[str]:
+        return ["10.0.0.5"]  # the name now points inside the network
+
+    monkeypatch.setattr(ssrf, "_resolve_all", resolve)
+    provider = ImapSmtpProvider(
+        ProviderConfig(
+            imap_host="imap.example.com",
+            imap_port=993,
+            imap_tls="ssl",
+            smtp_host="smtp.example.com",
+            smtp_port=465,
+            smtp_tls="ssl",
+            username="u",
+            password="p",
+            public_only=True,
+        )
+    )
+    with pytest.raises(ProviderConnectError):
+        await asyncio.wait_for(provider.verify(), 5)
+    with pytest.raises(ProviderConnectError):
+        await asyncio.wait_for(provider.send(b"x", "u@example.com", ["v@example.com"]), 5)

backend/tests/sync/test_secondary_poll.py

@@ -371,3 +371,68 @@ async def test_new_inbox_mail_while_live_asks_for_a_push(monkeypatch) -> None:
             await cleanup.execute(delete(User).where(User.id == user.id))
         await session.close()
         await engine.dispose()
+
+
+async def test_live_loop_catches_up_before_it_idles(monkeypatch) -> None:  # type: ignore[no-untyped-def]
+    """Mail that reached INBOX while the loop was not running (a new account's
+    first minutes, a reconnect) is fetched at once, not after the next new
+    message or the 10-minute IDLE timeout."""
+    import asyncio
+
+    engine = create_async_engine(get_settings().database_url, poolclass=NullPool)
+    sm = async_sessionmaker(engine, expire_on_commit=False)
+    session = sm()
+    user = User(handle=f"idl{uuid.uuid4().hex[:8]}@test.local", password_hash=hash_password("pw"))
+    session.add(user)
+    await session.flush()
+    account = Account(
+        user_id=user.id,
+        email="me@example.com",
+        imap_config={},
+        smtp_config={},
+        secret_ct=b"",
+        discovery_src="manual",
+    )
+    session.add(account)
+    await session.flush()
+    inbox = Mailbox(account_id=account.id, user_id=user.id, path="INBOX", special_use="inbox")
+    session.add(inbox)
+    await session.commit()
+
+    calls: list[str] = []
+    stop = asyncio.Event()
+
+    class FakeProvider:
+        async def verify(self) -> None:
+            return None
+
+        async def poll(self, mailbox: str, *, last_seen_uid: int, highestmodseq: int | None):  # type: ignore[no-untyped-def]
+            calls.append("poll")
+            waiting = RemoteMessage(
+                uid=1,
+                raw=_raw("Arrived while away", "<away@x.com>"),
+                flags=frozenset(),
+                internal_date=datetime.now(UTC),
+            )
+            return MailboxDelta([waiting] if len(calls) == 1 else [], [], [], None, None)
+
+        async def idle(self, mailbox: str) -> None:
+            calls.append("idle")
+            stop.set()
+
+        async def close(self) -> None:
+            return None
+
+    monkeypatch.setattr(sync_engine, "build_provider", lambda _a: FakeProvider())
+    try:
+        await asyncio.wait_for(sync_engine.live_loop(account.id, "INBOX", stop), 10)
+        assert calls == ["poll", "idle"]
+        n = await session.scalar(
+            select(func.count()).select_from(Message).where(Message.mailbox_id == inbox.id)
+        )
+        assert n == 1
+    finally:
+        async with session_scope() as cleanup:
+            await cleanup.execute(delete(User).where(User.id == user.id))
+        await session.close()
+        await engine.dispose()

docker-compose.yml

@@ -77,6 +77,8 @@ x-backend-env: &backend-env
   MAX_ATTACHMENT_MB: ${MAX_ATTACHMENT_MB:-25}
   TRASH_RETENTION_DAYS: ${TRASH_RETENTION_DAYS:-30}
   SENDER_AVATARS_ENABLED: ${SENDER_AVATARS_ENABLED:-true}
+  # New passwords checked against Have I Been Pwned (k-anonymity; docs §5.2).
+  PASSWORD_BREACH_CHECK: ${PASSWORD_BREACH_CHECK:-true}
   GOOGLE_OAUTH_ENABLED: ${GOOGLE_OAUTH_ENABLED:-false}
   OAUTH_GOOGLE_CLIENT_ID: ${OAUTH_GOOGLE_CLIENT_ID:-}
   OAUTH_GOOGLE_CLIENT_SECRET: ${OAUTH_GOOGLE_CLIENT_SECRET:-}

docker/Dockerfile.frontend

@@ -30,6 +30,7 @@ COPY docker/nginx.conf /etc/nginx/conf.d/default.conf
 # Shared server body, included by both listeners. Outside conf.d/ so nginx
 # does not try to load it as a config of its own.
 COPY docker/nginx-app.conf /etc/nginx/webmail-app.conf
+COPY docker/nginx-security.conf /etc/nginx/webmail-security.conf
 COPY --from=builder /src/dist /usr/share/nginx/html
 
 # Surface the running version to `deploy/webmail.sh status` without needing the API.

docker/nginx-app.conf

@@ -20,11 +20,10 @@ gzip_min_length 1024;
 gzip_types text/plain text/css application/javascript application/json
            image/svg+xml application/manifest+json;
 
-# Clickjacking / sniffing basics. The app's own CSP for mail HTML is applied
+# Security headers (CSP, framing, HSTS, …) for everything this listener serves.
-# server-side in app/indexer/sanitize.py; this is only the shell document.
+# Every location below that adds a header of its own includes the file again —
-add_header X-Content-Type-Options nosniff always;
+# see the note at the top of it.
-add_header X-Frame-Options SAMEORIGIN always;
+include /etc/nginx/webmail-security.conf;
-add_header Referrer-Policy no-referrer always;
 
 # ---- API ----------------------------------------------------------------
 location /api/ {
@@ -72,12 +71,14 @@ location ~ ^/\.well-known/(caldav|carddav)$ {
 location /assets/ {
     expires 1y;
     add_header Cache-Control "public, immutable";
+    include /etc/nginx/webmail-security.conf;
     try_files $uri =404;
 }
 
 location /fonts/ {
     expires 30d;
     add_header Cache-Control "public";
+    include /etc/nginx/webmail-security.conf;
     try_files $uri =404;
 }
 
@@ -85,6 +86,7 @@ location = /healthz {
     access_log off;
     return 200 "ok\n";
     add_header Content-Type text/plain;
+    include /etc/nginx/webmail-security.conf;
 }
 
 # The SPA fallback lives in each server block, not here: the two listeners serve
@@ -95,12 +97,14 @@ location = /healthz {
 # because the public listener 404s /admin.html before it can be served.
 location = /index.html {
     add_header Cache-Control "no-store, must-revalidate";
+    include /etc/nginx/webmail-security.conf;
 }
 
 # The offline-access service worker (frontend/public/sw.js): a fixed URL the
 # browser re-checks for a new version, so it must not be cached either.
 location = /sw.js {
     add_header Cache-Control "no-cache";
+    include /etc/nginx/webmail-security.conf;
     try_files $uri =404;
 }
 
@@ -110,5 +114,6 @@ location = /manifest.webmanifest {
     default_type application/manifest+json;
     types { }
     add_header Cache-Control "no-cache";
+    include /etc/nginx/webmail-security.conf;
     try_files $uri =404;
 }

docker/nginx-security.conf

@@ -0,0 +1,31 @@
+# Security headers for every response of the front door — the app shell, the
+# static files and the API alike.
+#
+# Included at server level by nginx-app.conf AND inside every location that
+# adds a header of its own: nginx drops ALL inherited add_header lines in a
+# location that has any add_header, which is how index.html once went out with
+# only its Cache-Control (security report, finding 1). A new location with an
+# add_header must include this file too.
+#
+# Content-Security-Policy, by directive:
+#   script-src 'self'    the Vite bundles, plugin bundles (/api/plugins/…) and
+#                        workers are all same-origin; no inline script, no eval
+#                        (pdf.js is told not to try).
+#   style-src            'unsafe-inline': React and the plugins set style
+#                        attributes, and message HTML carries its own <style>.
+#   img-src / font-src   https:/http: because an email whose images the user
+#                        chose to load fetches them from the sender's servers
+#                        (the message frame is srcdoc, so it shares this policy).
+#   connect-src          the API and the live-update WebSocket on this host
+#                        ($http_host: with the port, for LAN access on WEB_PORT).
+#   frame-ancestors      'self', not 'none': printing an attachment loads it in
+#                        a hidden frame of our own. No other site may frame us.
+add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: blob: https: http:; font-src 'self' data: https:; media-src 'self' blob:; connect-src 'self' wss://$http_host ws://$http_host; worker-src 'self' blob:; frame-src 'self' blob:; manifest-src 'self'; object-src 'none'; base-uri 'self'; form-action 'self'; frame-ancestors 'self'" always;
+add_header X-Frame-Options SAMEORIGIN always;
+add_header X-Content-Type-Options nosniff always;
+add_header Referrer-Policy no-referrer always;
+add_header Permissions-Policy "camera=(), microphone=(), geolocation=(), payment=(), usb=()" always;
+# Only on requests that reached the reverse proxy over HTTPS ($hsts is empty
+# otherwise, and nginx sends no header with an empty value): plain-HTTP LAN
+# access on WEB_PORT keeps working.
+add_header Strict-Transport-Security $hsts always;

docker/nginx.conf

@@ -28,6 +28,15 @@ map $http_x_forwarded_proto $fwd_proto {
     http    http;
 }
 
+# HSTS only for requests that came in over HTTPS (nginx-security.conf).
+map $fwd_proto $hsts {
+    https   "max-age=31536000";
+    default "";
+}
+
+# No nginx version in the Server header or on error pages.
+server_tokens off;
+
 # Connection header for the WebSocket upgrade dance on /api/ws.
 map $http_upgrade $connection_upgrade {
     default upgrade;
@@ -44,6 +53,13 @@ server {
     listen 80;
     server_name _;
 
+    # The reverse proxy in front (DSM) terminates TLS and says how the browser
+    # came in. Plain HTTP from the internet goes to HTTPS; a request with no
+    # such header (LAN access straight to WEB_PORT) is left alone.
+    if ($http_x_forwarded_proto = "http") {
+        return 301 https://$host$request_uri;
+    }
+
     # Regex locations beat prefix ones, so this wins over `location /api/`
     # regardless of order. `(/|$)` keeps it to /api/admin and /api/admin/...,
     # never a future /api/administrators. 404 rather than 403: a port open to
@@ -76,6 +92,7 @@ server {
 
     location = /admin.html {
         add_header Cache-Control "no-store, must-revalidate";
+        include /etc/nginx/webmail-security.conf;
     }
 
     # SPA fallback -> the admin panel. `/` on this port IS the panel; the mail

docs/nas-install.md

@@ -569,6 +569,24 @@ Session cookies get the `Secure` and `__Host-` treatment automatically as soon
 as the app sees an HTTPS request: nginx forwards `X-Forwarded-Proto`, and the
 API is started with `--proxy-headers`. Nothing to configure.
 
+**Plain HTTP and HSTS.** If DSM also has a rule for **HTTP** / port 80 to the
+same hostname, keep it: the web container answers any request DSM forwarded
+over plain HTTP with a `301` to `https://` (it recognises one by DSM's
+`X-Forwarded-Proto: http`), and sends `Strict-Transport-Security` on HTTPS
+responses. Leave DSM's own *Enable HSTS* box unticked — the container already
+sends the header. Opening `http://NAS:8088` on the LAN is not redirected
+(no reverse proxy, no such header).
+
+**Security headers** (CSP, framing, `nosniff`, referrer, HSTS) are set by the
+web container on every response — `docker/nginx-security.conf`. Don't add
+Custom Headers for them in DSM: two differing CSPs are both enforced.
+
+**Breached-password check.** New passwords (sign-up, reset) are checked
+against Have I Been Pwned's range API — only the first 5 hex digits of the
+password's SHA-1 leave the server. The API container needs outbound HTTPS to
+`api.pwnedpasswords.com`; when it cannot reach it the check is skipped, never
+fatal. `PASSWORD_BREACH_CHECK=false` turns it off.
+
 ### 5.3 Installing as an app, and notifications about new mail
 
 Over HTTPS the web app is installable (Chrome/Edge: the install icon in the

frontend/src/components/list/MessageList.tsx

@@ -31,6 +31,8 @@ function initials(p: Address | undefined): string {
 }
 
 // Past this many characters the sender column switches to first names only.
+// List width (px) below which rows stack instead of using one line.
+const STACK_BELOW = 560;
 const SENDERS_FULL_MAX = 25;
 // A lone sender's name longer than this is cut to one character less plus "...".
 const SINGLE_SENDER_MAX = 22;
@@ -119,6 +121,11 @@ export function MessageList({
 }) {
   const t = useT();
   const parentRef = useRef<HTMLDivElement>(null);
+  // A list narrower than this has no room for the one-line row (a 200px sender
+  // column and the action rail would leave the subject no width at all): it
+  // stacks sender, subject and snippet as on a phone.
+  const [narrow, setNarrow] = useState(false);
+  const stacked = compact || narrow;
   const swipe = useSwipeToDelete(onSwipeDelete);
   // In Trash/Spam/Archive the middle action restores; elsewhere it archives.
   const isRemovalFolder = folder === "trash" || folder === "junk" || folder === "archive";
@@ -162,6 +169,15 @@ export function MessageList({
     parentRef.current?.scrollTo({ top: 0 });
   }, [page]);
 
+  const empty = threads.length === 0;
+  useEffect(() => {
+    const el = parentRef.current;
+    if (!el) return;
+    const ro = new ResizeObserver(() => setNarrow(el.clientWidth < STACK_BELOW));
+    ro.observe(el);
+    return () => ro.disconnect();
+  }, [empty]);
+
   if (threads.length === 0) {
     return <div className="p-6 text-[15px] text-app-faint">{t("mail.noConversations")}</div>;
   }
@@ -309,7 +325,7 @@ export function MessageList({
                   </button>
                 </div>
 
-                {compact ? (
+                {stacked ? (
                   <div className="flex min-w-0 flex-1 flex-col justify-center">
                     <div className="flex min-w-0 items-center gap-1.5">
                       <span
@@ -324,7 +340,11 @@ export function MessageList({
                           {thread.message_count}
                         </span>
                       )}
-                      <span className="ml-auto flex shrink-0 items-center gap-1.5 pl-2 text-app-faint">
+                      <span
+                        className={`ml-auto flex shrink-0 items-center gap-1.5 pl-2 text-app-faint ${
+                          compact ? "" : "group-hover:hidden"
+                        }`}
+                      >
                         {thread.has_attachments && <Paperclip />}
                         {thread.pinned && (
                           <Icon name="pin" size={15} className="text-[rgb(220_129_143)]" />
@@ -337,6 +357,50 @@ export function MessageList({
                           {timeLabel(thread.last_message_at)}
                         </span>
                       </span>
+                      {/* A narrow desktop list: the actions take the date's place on hover. */}
+                      {!compact && (
+                        <span className="ml-auto hidden shrink-0 items-center gap-3 pl-2 group-hover:flex">
+                          <button
+                            type="button"
+                            title={thread.pinned ? t("mail.unpin") : t("mail.pin")}
+                            onClick={stop(() => onTogglePin(thread.id, thread.pinned))}
+                            className={`wm-online-only ${
+                              thread.pinned ? "text-[rgb(220_129_143)]" : "text-app-muted hover:text-app-fg"
+                            }`}
+                          >
+                            <Icon name="pin" size={16} />
+                          </button>
+                          {isRemovalFolder ? (
+                            <button
+                              type="button"
+                              title={t("mail.restore")}
+                              onClick={stop(() => onRestore(thread.id))}
+                              className="wm-online-only text-app-muted hover:text-app-fg"
+                            >
+                              <Icon name="restore" size={16} />
+                            </button>
+                          ) : (
+                            <button
+                              type="button"
+                              title={t("mail.archive")}
+                              onClick={stop(() => onArchive(thread.id))}
+                              className="wm-online-only text-app-muted hover:text-app-fg"
+                            >
+                              <Icon name="archive" size={14} />
+                            </button>
+                          )}
+                          <button
+                            type="button"
+                            title={t("mail.delete")}
+                            onClick={stop(() =>
+                              folder === "trash" ? onDeletePermanent(thread.id) : onTrash(thread.id),
+                            )}
+                            className="wm-online-only text-app-muted hover:text-app-fg"
+                          >
+                            <Icon name="trash" size={16} />
+                          </button>
+                        </span>
+                      )}
                     </div>
                     <div
                       className={`flex min-w-0 items-center gap-1.5 text-[14px] ${

frontend/src/components/thread/AttachmentPreview.tsx

@@ -532,7 +532,8 @@ function PdfView({
       try {
         const buf = await (await fetch(url, { credentials: "include" })).arrayBuffer();
         if (cancelled) return;
-        const doc = await pdfjs.getDocument({ data: buf, password }).promise;
+        // No eval: the Content-Security-Policy forbids it (docker/nginx-security.conf).
+        const doc = await pdfjs.getDocument({ data: buf, password, isEvalSupported: false }).promise;
         if (cancelled) return;
         docRef.current = doc;
         setNeedPassword(false);

frontend/src/components/thread/Attachments.tsx

@@ -351,6 +351,8 @@ export function Attachments({ messageId }: { messageId: string }) {
           />
         ))}
       </div>
+      {/* One file has its own download button: a zip of it would add nothing. */}
+      {attachments.length > 1 && (
       <div className="mt-2">
         <a
           href={api.attachmentsZipUrl(messageId)}
@@ -360,6 +362,7 @@ export function Attachments({ messageId }: { messageId: string }) {
           {t("mail.downloadAll", { count: attachments.length })}
         </a>
       </div>
+      )}
       {previewIdx !== null && (
         <Suspense fallback={null}>
           <AttachmentPreview

frontend/src/components/thread/MessageBody.tsx

@@ -6,6 +6,7 @@ import { api } from "../../lib/api";
 import { adaptForDarkMode, useDarkMessages, withDarkPage } from "../../lib/darkMessage";
 import { fixInvisibleText } from "../../lib/readability";
 import { useTheme } from "../../lib/theme";
+import { useIsMobile } from "../../lib/useIsMobile";
 import type { MessageEnvelope } from "../../lib/types";
 import { Attachments } from "./Attachments";
 
@@ -38,6 +39,8 @@ export function MessageBody({
   const dark = useTheme().resolved === "dark" && darkMessages;
   const darkRef = useRef(dark);
   darkRef.current = dark;
+  const mobileRef = useRef(false);
+  mobileRef.current = useIsMobile();
 
   const { data, isLoading, isError, error } = useQuery({
     queryKey: ["message-html", message.id, allowed],
@@ -64,13 +67,15 @@ export function MessageBody({
     // Float-accurate content bottom (getBoundingClientRect keeps sub-pixels that
     // scrollHeight would floor), combined with the integer scroll/offset heights.
     const rectBottom = body ? body.getBoundingClientRect().bottom : 0;
+    // The body's own heights are before a phone's fit-to-width scaling (below).
+    const zoom = Number(body?.style.zoom) || 1;
     let h = Math.ceil(
       Math.max(
         rectBottom,
         de.scrollHeight,
         de.offsetHeight,
-        body?.scrollHeight ?? 0,
+        (body?.scrollHeight ?? 0) * zoom,
-        body?.offsetHeight ?? 0,
+        (body?.offsetHeight ?? 0) * zoom,
       ),
     );
     // If the email overflows horizontally, its bottom scrollbar steals vertical
@@ -81,6 +86,26 @@ export function MessageBody({
     setHeight(h);
   }, []);
 
+  // Phone: an email laid out wider than the screen (a fixed-width table, one
+  // long file name that must not wrap) is scaled down to fit, as phone mail
+  // apps do, instead of being cut off at the right edge. Its no-wrap cells may
+  // then wrap, so one long name no longer squeezes the other columns to a
+  // letter per line. On a desktop a wide email scrolls sideways, as before.
+  const fitWidth = useCallback((doc: Document) => {
+    const de = doc.documentElement;
+    const body = doc.body;
+    if (!body) return;
+    body.style.zoom = "";
+    doc.getElementById("wm-fit")?.remove();
+    if (!mobileRef.current || de.scrollWidth <= de.clientWidth + 1) return;
+    const scale = Math.max(0.5, de.clientWidth / de.scrollWidth);
+    const relax = doc.createElement("style");
+    relax.id = "wm-fit";
+    relax.textContent = "td,th{white-space:normal!important}";
+    doc.head.appendChild(relax);
+    body.style.zoom = String(scale);
+  }, []);
+
   // Hide the quoted original by default and drop a "•••" toggle right after the
   // "On <date>, <sender> wrote:" attribution (inside the white body), so the reader
   // sees only the new content until they choose to reveal the quote.
@@ -148,6 +173,7 @@ export function MessageBody({
       fixInvisibleText(doc); // white-on-white from a dark-mode sender (lib/readability.ts)
     }
     injectQuoteToggle(doc);
+    fitWidth(doc);
     resize();
     // Re-measure after the first paint settles (fonts/layout can shift the height
     // by a hair, which is enough to leave a spurious scrollbar).
@@ -171,9 +197,22 @@ export function MessageBody({
     const doc = frameRef.current?.contentDocument;
     if (!doc) return;
     prepare(doc);
+    fitWidth(doc); // images may have widened it
     resize(); // everything has loaded: one last measure
   };
 
+  // A phone turned sideways: fit to the new width.
+  useEffect(() => {
+    const refit = () => {
+      const doc = frameRef.current?.contentDocument;
+      if (preparedRef.current !== doc || !doc) return;
+      fitWidth(doc);
+      resize();
+    };
+    window.addEventListener("resize", refit);
+    return () => window.removeEventListener("resize", refit);
+  }, [fitWidth, resize]);
+
   // Watch for the message's document to be parsed (the frame starts on an
   // empty about:blank document, which does not count).
   useEffect(() => {

frontend/src/i18n/en.ts

@@ -130,6 +130,7 @@ export const en = {
   "mail.selectAll": "Select all",
   "mail.conversationSelected": "1 conversation selected",
   "mail.conversationsSelected": "{count} conversations selected",
+  "mail.conversationsSelected_one": "1 conversation selected",
   "mail.alsoIn": "Also delivered to",
   "mail.emptyTrash": "Empty trash",
   "mail.emptySpam": "Empty spam",
@@ -201,6 +202,7 @@ export const en = {
   "mail.hideQuoted": "Hide quoted text",
   "mail.markReadUnread": "Mark read / unread",
   "mail.messageCount": "{count} messages",
+  "mail.messageCount_one": "1 message",
   "mail.downloadAll": "Download all {count} attachments",
   "mail.downloadZip": "Download zip",
   "mail.download": "Download",
@@ -218,6 +220,7 @@ export const en = {
   "compose.closePrompt": "Save this message as a draft?",
   "compose.sent": "Message sent.",
   "compose.undoIn": "{count} seconds to",
+  "compose.undoIn_one": "1 second to",
   "compose.undo": "Undo",
   "compose.sendFailed": "Send failed.",
   "compose.savingDraft": "Saving draft…",
@@ -419,6 +422,7 @@ export const en = {
   "appPasswords.created": "Created {date}",
   "appPasswords.lastUsed": "last used {date}",
   "appPasswords.neverUsed": "never used",
+  "appPasswords.lastUsedDav": "calendars or contacts last synced {date}",
   "appPasswords.confirmRevoke": "Revoke the app password “{name}”? The app using it will stop signing in.",
   "settings.thisDevice": "this device",
   "settings.revoke": "Revoke",
@@ -474,6 +478,7 @@ export const en = {
   "settings.icloudHint":
     "Use an app-specific password from account.apple.com → Sign-In and Security.",
   "settings.calendarCount": "{count} calendars",
+  "settings.calendarCount_one": "1 calendar",
   "settings.removeSubscription": "Remove subscription",
   "settings.removeSubscriptionConfirm": "Stop syncing “{name}” and remove its events?",
   "settings.deleteCalendar": "Delete calendar",
@@ -597,6 +602,7 @@ export const en = {
   "offline.folderNotSaved": "This folder isn't saved on this device.",
   "offline.noticeScheduled": "Saved to Scheduled — it will be sent when you're back online.",
   "offline.noticeSendingScheduled": "Sending {count} scheduled messages…",
+  "offline.noticeSendingScheduled_one": "Sending 1 scheduled message…",
   "offline.draftsNotSaved": "Only drafts written on this device are available offline.",
   "compose.sendLater": "Schedule",
   "compose.savedOnDevice": "Saved on this device",
@@ -615,6 +621,8 @@ export const en = {
   "scheduled.delete": "Delete",
   "scheduled.statusRetrying":
     "The mail server couldn't take this message yet ({count} tries). Next try {when}; it keeps trying until {until}.",
+  "scheduled.statusRetrying_one":
+    "The mail server couldn't take this message yet (1 try). Next try {when}; it keeps trying until {until}.",
   "scheduled.statusFailed": "Not sent: {error}",
   "scheduled.lastError": "Last error: {error}",
   "scheduled.to": "To",
@@ -631,7 +639,9 @@ export const en = {
   "offline.settingHelp":
     "Keep your newest 100 Inbox conversations, and the ones you open, on this device, so you can read them without a connection. They are stored unencrypted in this browser and removed when you sign out — leave this off on shared computers.",
   "offline.settingStatus": "{count} conversations saved · {size} · updated {when}",
+  "offline.settingStatus_one": "1 conversation saved · {size} · updated {when}",
   "offline.settingStatusNoTime": "{count} conversations saved · {size}",
+  "offline.settingStatusNoTime_one": "1 conversation saved · {size}",
   "offline.settingSaving": "Saving recent mail…",
   "offline.settingUnsupported":
     "Not available here: browsers allow offline access only when the app is opened over HTTPS.",

frontend/src/i18n/index.tsx

@@ -35,7 +35,15 @@ export function I18nProvider({ children }: { children: ReactNode }) {
 
   const value = useMemo<I18nContextValue>(() => {
     const catalog = catalogs[locale] ?? en;
-    const t: TFunc = (key, vars) => interpolate(catalog[key] ?? en[key] ?? key, vars);
+    // A count of exactly one picks the "<key>_one" form where there is one
+    // ("1 message", not "1 messages").
+    const lookup = (key: string): string | undefined =>
+      (catalog as Record<string, string>)[key] ?? (en as Record<string, string>)[key];
+    const t: TFunc = (key, vars) =>
+      interpolate(
+        (vars?.count === 1 ? lookup(`${key}_one`) : undefined) ?? lookup(key) ?? key,
+        vars,
+      );
     return {
       locale,
       setLocale: (l) => {

frontend/src/routes/settings/Settings.tsx

@@ -630,10 +630,14 @@ function AppPasswordsSetting() {
               <span className="min-w-0">
                 <span className="break-words">{a.name}</span>
                 <span className="block text-xs text-app-faint">
-                  {t("appPasswords.created", { date: date(a.created_at) })} ·{" "}
+                  {t("appPasswords.created", { date: date(a.created_at) })}
+                  {/* Only calendar and contacts sign-ins are seen here: the mail
+                      server checks IMAP/SMTP ones itself and keeps no record. */}
                   {a.last_used_at
-                    ? t("appPasswords.lastUsed", { date: date(a.last_used_at) })
+                    ? ` · ${t(mailHost ? "appPasswords.lastUsedDav" : "appPasswords.lastUsed", { date: date(a.last_used_at) })}`
-                    : t("appPasswords.neverUsed")}
+                    : mailHost
+                      ? ""
+                      : ` · ${t("appPasswords.neverUsed")}`}
                 </span>
               </span>
               <button

frontend/src/test/i18n.test.tsx

@@ -0,0 +1,24 @@
+// A count of one reads in the singular ("1 message"), any other in the plural.
+
+import { renderHook } from "@testing-library/react";
+import type { ReactNode } from "react";
+import { describe, expect, it } from "vitest";
+
+import { I18nProvider, useT } from "../i18n";
+
+const wrapper = ({ children }: { children: ReactNode }) => <I18nProvider>{children}</I18nProvider>;
+
+describe("t()", () => {
+  it("uses the singular form for a count of one", () => {
+    const { result } = renderHook(() => useT(), { wrapper });
+    const t = result.current;
+    expect(t("mail.messageCount", { count: 1 })).toBe("1 message");
+    expect(t("mail.messageCount", { count: 2 })).toBe("2 messages");
+    expect(t("mail.messageCount", { count: 0 })).toBe("0 messages");
+  });
+
+  it("falls back to the plain string where there is no singular", () => {
+    const { result } = renderHook(() => useT(), { wrapper });
+    expect(result.current("mail.downloadAll", { count: 1 })).toBe("Download all 1 attachments");
+  });
+});

frontend/vite.config.ts

@@ -25,6 +25,9 @@ export default defineConfig({
         target: "http://127.0.0.1:8000",
         changeOrigin: true,
         ws: true,
+        // X-Forwarded-Host: the API's cross-site check (app/security/cross_site.py)
+        // compares the page's Origin with the name the browser used.
+        xfwd: true,
       },
       // CalDAV / CardDAV (SPEC Appendix E), for trying clients against dev.
       "/dav": { target: "http://127.0.0.1:8000", changeOrigin: true },