zot is a production-ready vendor-neutral OCI image registry. The group data stored for users in the boltdb database (meta.db) is an append-list so group revocations/removals are ignored in the API. SetUserGroups is alled on login, but instead of replacing the group memberships, they are appended. This may be due to some conflict with the group definitions in the config file, but that wasn't obvious to me if it were the case. Any Zot configuration that relies on group-based authorization will not respect group remove/revocation by an IdP. This issue has been addressed in version 2.1.2. All users are advised to upgrade. There are no known workarounds for this vulnerability.