Tutor LMS <= 2.7.6 is vulnerable to User Registration Setting Bypass to Unauthorized User Registration vulnerability

The Tutor LMS plugin for WordPress is vulnerable to bypass to user registration in versions up to, and including, 2.7.6. This is due to a missing check for the 'users_can_register' option in the 'register_instructor' function. This makes it possible for unauthenticated attackers to register as the default role on the site, even if registration is disabled.