Impact The FiftyOne App/API server ("fiftyone/server/app.py") and the "/media" route ("fiftyone/server/routes/media.py") unconditionally set a permissive CORS header ("Access-Control-Allow-Origin: *") on their responses. Because the embedded App server runs locally and is unauthenticated, this allows any website a user visits to make cross-origin requests to that user's running FiftyOne server and read the responses. Combined with the unauthenticated "/media" endpoint — which serves files from the local filesystem by path — the wildcard CORS policy turns a local-only file read into a remotely exploitable, drive-by data exfiltration vulnerability. A malicious web page can silently issue requests such as "http://localhost:5151/media?filepath=/etc/passwd" and read arbitrary files accessible to the server process (SSH keys, cloud credentials, ".env" files, dataset media, etc.), then exfiltrate them to an attacker-controlled endpoint. The victim only needs to have a FiftyOne server running locally and visit a malicious page — no clicks or other interaction are required. Browsers that have shipped Private Network Access / local-network-access protections (e.g. Chromium 142+) mitigate this for some users, but Safari and Firefox do not yet, so the attack remains viable in common configurations. Who is impacted: any user running FiftyOne (the open-source, embedded App server) locally while also browsing the web. Not affected: media stored in cloud buckets, which is served via signed URLs on a separate origin. Patches Fixed in FiftyOne 1.17.0. The hard-coded "Access-Control-Allow-Origin: " has been removed and the server now responds same-origin only by default, which covers local desktop usage and the supported notebook integrations (each served through a same-origin proxy or iframe). Cross-origin access is now opt-in via a new "allowed_origins" config option (environment variable "FIFTYONE_ALLOWED_ORIGINS"), an explicit comma-separated list of trusted origins, e.g.: export FIFTYONE_ALLOWED_ORIGINS='https://app.example.com,http://localhost:3000' The literal value "" restores the legacy wildcard behavior for users who explicitly require it and emits a warning. Users should upgrade to FiftyOne 1.17.0 or later. Workarounds In affected versions there is no configuration flag to disable the wildcard CORS header without upgrading. Until you can upgrade: - Do not run the FiftyOne App server while browsing untrusted websites. - Keep the App server bound to "localhost" (the default) and avoid exposing it on a network interface. - Use a browser that enforces Private Network Access protections. Resources - OWASP A01:2025 – Broken Access Control: https://owasp.org/Top10/2025/A01_2025-Broken_Access_Control/