The User Registration & Membership – Custom Registration Form, Login Form, and User Profile plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 4.2.1 via the create_stripe_subscription() function, due to missing validation on the 'member_id' user controlled key. This makes it possible for unauthenticated attackers to delete arbitrary user accounts that have registered through the plugin.
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.