wger is a free, open-source workout and fitness manager. Five routine detail action endpoints check a cache before calling "self.get_object()". In versions up to and including 2.4, ache keys are scoped only by "pk" — no user ID is included. When a victim has previously accessed their routine via the API, an attacker can retrieve the cached response for the same PK without any ownership check. Commit e964328784e2ee2830a1991d69fadbce86ac9fbf contains a patch for the issue.