This module enables you to turn a Drupal install into the Central Authentication System (CAS) Server. It makes your database the primary location for other systems to use for authentication in a SSO environment. The module doesn't sufficiently check the service URL used to redirect the user during logout, leading to an open redirect. This vulnerability is mitigated by the fact that an attacker must convince a user to click a specially crafted link. The vulnerability cannot be exploited without user interaction and does not allow an attacker to directly compromise the CAS server or bypass authentication.