Tautulli is a Python based monitoring and tracking tool for Plex Media Server. Versions prior to 2.17.1 expose configUpdate as a state-changing administrator endpoint, but the route does not enforce POST and does not use any anti-CSRF token. In the default form and JWT-based authentication mode, the administrator session cookie is issued with SameSite=Lax, which still permits top-level cross-site navigation requests. An attacker can exploit this by luring a logged-in administrator to a malicious page that submits a cross-site request to /configUpdate and overwrites the local administrator username and password. The attacker can then sign in directly with the chosen credentials and take over the Tautulli administrative interface. Version 2.17.1 patches the issue.