User Registration & Membership <= 5.2.0 - Missing Authorization to Unauthenticated Payment Bypass

The User Registration & Membership – Free & Paid Memberships, Subscriptions, Content Restriction, User Profile, Custom User Registration & Login Builder plugin for WordPress is vulnerable to unauthorized modification of data due to missing validation checks in the confirm_payment() function in all versions up to, and including, 5.2.0. This makes it possible for unauthenticated attackers to bypass payment processing and activate paid memberships.