GHSA-f24x-5g9q-753f OAuth2 Proxy's session cookies are not cleared when rendering sign-in page

• Go github.com/oauth2-proxy/oauth2-proxy/v7: >= 7.11.0, < 7.15.2 → fixed in 7.15.2

Impact A regression introduced in v7.11.0 is preventing OAuth2 Proxy from clearing the session cookie when rendering the sign-in page. This only impacts deployments that rely on the sign-in page as part of their logout flow. In those setups, a user may be shown the sign-in page while the existing session cookie remains valid, so the browser session is not actually logged out. On shared workstations be it browsers or devices, a subsequent user could continue to use the previous user's authenticated session. Deployments that use a dedicated logout/sign-out endpoint to terminate sessions are not affected. Patches This issue is fixed in v7.15.2. Workarounds Do not rely on the sign-in page to clear an existing session. Instead: • Use the dedicated logout/sign-out endpoint of OAuth2 Proxy • Ensure your application logout flow explicitly clears the OAuth2 Proxy session cookie before redirecting users to the sign-in page • If needed, clear the session cookie at the reverse proxy or application layer as a temporary mitigation