A privilege escalation vulnerability has been identified in Umbraco CMS affecting versions from 15.3.1 to before 16.5.1 and 17.2.2. The vulnerability allows authenticated backoffice users with permission to manage users to elevate their privileges due to insufficient authorization enforcement when modifying user group memberships. The affected functionality does not properly validate whether a user has sufficient privileges to assign highly privileged roles. This security flaw has been fixed in versions 16.5.1 and 17.2.2.