Parse Server before 8.6.112 and 9.0.0 before 9.10.6-alpha.4 contains an authorization bypass in the session upgrade endpoint, which creates a new session for any valid session token without enforcing the _Session class create class-level permission. Attackers holding a user's session token can send an already revocable token to /upgradeToRevocableSession to obtain additional sessions with fresh expiration that persist after the original session is logged out.