The FiftyOne App/API server in versions before 1.17.0 unconditionally returns Access-Control-Allow-Origin: * headers, enabling any website visited by the user to perform cross-origin reads of local server data. The /media endpoint accepts a filesystem path parameter, which can be exploited by a malicious webpage to read arbitrary files accessible to the server process and exfiltrate their contents without further user interaction. The vulnerability arises from improper CORS configuration and lack of authentication on the embedded local server. The issue is resolved in version 1.17.0 by introducing the allowed_origins configuration option and the FIFTYONE_ALLOWED_ORIGINS environment variable, which restrict cross-origin access to explicit origins and default to a same-origin policy.

An attacker can exploit this vulnerability by tricking a user into visiting a malicious website, which can then read sensitive local files served by the FiftyOne App's /media endpoint via cross-origin requests. This leads to confidentiality loss of local data accessible to the server process. The vulnerability does not allow modification or denial of service but can expose high-value local files without user consent beyond visiting the malicious page.

This vulnerability is fixed in FiftyOne App version 1.17.0. Users should upgrade to version 1.17.0 or later to ensure cross-origin access is properly restricted. The fix introduces explicit allowed_origins configuration and environment variables to control CORS policies, defaulting to same-origin. No additional mitigation is required once upgraded.