A flaw was found in Keycloak. An IDOR (Broken Access Control) vulnerability exists in the admin API endpoints for authorization resource management, specifically in ResourceSetService and PermissionTicketService. The system checks authorization against the resourceServer (client) ID provided in the API request, but the backend database lookup and modification operations (findById, delete) only use the resourceId. This mismatch allows an authenticated attacker with fine-grained admin permissions for one client (e.g., Client A) to delete or update resources belonging to another client (Client B) within the same realm by supplying a valid resource ID.