LearnPress <= 4.2.6.8.1 is vulnerable to Unauthenticated Bypass to User Registration vulnerability

The LearnPress – WordPress LMS Plugin plugin for WordPress is vulnerable to unauthenticated bypass to user registration in versions up to, and including, 4.2.6.8.1. This is due to missing checks in the 'check_validate_fields' function in the checkout. This makes it possible for unauthenticated attackers to register as the default role on the site, even if registration is disabled.