The User Registration & Membership WordPress plugin before 5.2.8 does not properly restrict who may author a membership plan or validate the plan a user attaches to their own account, allowing authenticated users with Author-level access and above to assign themselves an arbitrary role and escalate their privileges to Administrator.
https://wpscan.com/vulnerability/a4fbdeea-0d3b-466b-b4b6-4c4db277cd1d/