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, 4.1.3 via the user_registration_update_profile_details() due to missing validation on the 'user_id' user controlled key. This makes it possible for unauthenticated attackers to update other user's passwords, if they have access to the user ID and email.
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.