[bug]: live server CORS falls back to origin [""] instead of false, short-circuiting every OPTIONS request

[Hayyan612]

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

When CORS_ALLOWED_ORIGINS is unset, the live server is meant to deny all cross-origin
requests via origin: false. That branch is unreachable, and what it falls back to
instead changes how the server answers every OPTIONS request.

apps/live/src/server.ts:71-81:

const allowedOrigins = env.CORS_ALLOWED_ORIGINS.split(",").map((s) => s.trim());
this.app.use(
  cors({
    origin: allowedOrigins.length > 0 ? allowedOrigins : false,
    credentials: true,
    ...

CORS_ALLOWED_ORIGINS defaults to "" at apps/live/src/env.ts:19, and "".split(",")
returns [""], not []. Length is 1, so allowedOrigins.length > 0 is always true and
the : false branch can never run. origin is set to [""].

The two are not equivalent. In cors, a falsy origin means the middleware calls
next() without touching the response, so OPTIONS reaches your router. A truthy array
means it runs the full preflight path and answers OPTIONS itself with
optionsSuccessStatus, which defaults to 204.

Measured on cors@2.8.6 / express@5.2.1 with the exact options from server.ts:

origin:false  OPTIONS -> 200  (no cors headers)
origin:false  POST    -> 200  (no cors headers)
origin:[""]   OPTIONS -> 204  access-control-allow-credentials: true |
                              access-control-allow-headers: Content-Type,Authorization,x-api-key |
                              access-control-allow-methods: GET,POST,PUT,DELETE,OPTIONS |
                              vary: Origin
origin:[""]   POST    -> 200  access-control-allow-credentials: true | vary: Origin

So today, on a default install:

• every OPTIONS to any /live/* route is swallowed by the CORS middleware and answered
  204, instead of reaching the router or the 404 handler in setupNotFoundHandler
• preflights advertise Access-Control-Allow-Credentials: true along with the allowed
  methods and headers, for an origin list that allows nothing
• every response carries Vary: Origin and Access-Control-Allow-Credentials: true

To be clear about severity: no Access-Control-Allow-Origin is ever emitted, so browsers
still block the cross-origin read. This is not a vulnerability. It is the server
advertising a CORS posture it does not have, and answering a method it did not intend to
handle.

There is a second half to this. CORS_ALLOWED_ORIGINS never reaches the live container in
a compose deploy. In deployments/cli/community/docker-compose.yml it is defined at line
52 inside the x-app-env anchor, while the live service takes
<<: [*live-env, *redis-env], and x-live-env at line 45 holds only API_BASE_URL and
LIVE_SERVER_SECRET_KEY. apps/live/.env.example does not list it either. So the knob
cannot currently be set for the live server at all, which is why the empty-string path is
the one everybody is on.

Worth knowing while fixing it: cors only honours "*" as a wildcard when origin is a
bare string. Inside an array it is compared with origin === allowedOrigin, so once the
variable is plumbed through, CORS_ALLOWED_ORIGINS=* would deny everything rather than
allow it.

The Django side already gets all of this right, and comments the reason.
apps/api/plane/settings/common.py:182-186:

cors_origins_raw = os.environ.get("CORS_ALLOWED_ORIGINS", "")
# filter out empty strings
cors_allowed_origins = [origin.strip() for origin in cors_origins_raw.split(",") if origin.strip()]
if cors_allowed_origins:
    CORS_ALLOWED_ORIGINS = cors_allowed_origins
else:
    CORS_ALLOW_ALL_ORIGINS = True

Steps to reproduce

No Plane instance needed, the parse is the whole bug:

node -e 'console.log(JSON.stringify("".split(",")))'   # => [""]  , length 1, not []

To see the behavioural difference, stand up two Express apps with the options from
server.ts, one with origin: false and one with origin: [""], and send an OPTIONS
with an Origin header to each. The first returns 200 from the route with no CORS
headers; the second returns 204 from the CORS middleware with credentials, methods and
headers advertised.

On a real deployment:

1. Start a community compose deployment from deployments/cli/community with
   CORS_ALLOWED_ORIGINS set in variables.env.
2. docker compose exec live env | grep CORS — the variable is absent.
3. curl -i -X OPTIONS -H 'Origin: https://example.com' https://<host>/live/health —
   204 with Access-Control-Allow-Credentials: true, rather than the route's response.

Environment

Deploy preview

Edition

Community

Version

v1.4.2, also present on preview as of 15 Sep 2026

---

Suggested fix

Mirror the filter the Django settings already use, so the intended false is reachable:

const allowedOrigins = env.CORS_ALLOWED_ORIGINS.split(",")
  .map((s) => s.trim())
  .filter(Boolean);

origin: allowedOrigins.length > 0 ? allowedOrigins : false,

and plumb the variable through so the knob works at all: add
CORS_ALLOWED_ORIGINS: ${CORS_ALLOWED_ORIGINS} to x-live-env in
deployments/cli/community/docker-compose.yml, and add it to apps/live/.env.example.

Happy to open a PR for this if it is wanted.