CVE-2025-55008: 
JavaScript vulnerability analysis and mitigation

The CVE-2025-55008 affects the AuthKit library for React Router 7+, specifically versions 0.6.1 and below of @workos-inc/authkit-react-router. The vulnerability was discovered and disclosed on August 8, 2025, involving the exposure of sensitive authentication artifacts. The library, which provides helpers for authentication and session management using WorkOS & AuthKit with React Router, inadvertently exposed sensitive authentication data - specifically sealedSession and accessToken - by returning them from the authkitLoader, causing them to be rendered in the browser HTML (GitHub Advisory).

The vulnerability is classified with a CVSS v3.1 base score of 7.1 (High), with the vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L. The technical issue stems from the authkitLoader function returning sensitive authentication artifacts (sealedSession and accessToken) in its response, which were then rendered into the browser's HTML output. This implementation flaw exposed critical authentication data that should have remained server-side (GitHub Advisory).

The exposure of sensitive authentication artifacts could lead to session hijacking in environments where cross-site scripting (XSS), malicious browser extensions, or local inspection is possible. This vulnerability potentially allows attackers to gain unauthorized access to user sessions and impersonate legitimate users (GitHub Advisory).

The vulnerability has been patched in version 0.7.0 of @workos-inc/authkit-react-router. In the patched version, sealedSession and accessToken are no longer returned by default from the authkitLoader, and a secure server-side mechanism is provided to fetch an access token as needed. Users should upgrade to version 0.7.0 or later to address this security issue (GitHub Release).