The WPGYM - Wordpress Gym Management System plugin for WordPress is vulnerable to privilege escalation in all versions up to, and including, 67.7.0 via the 'MJ_gmgt_gmgt_add_user' function due to missing validation on a user controlled key. This makes it possible for authenticated attackers, with Subscriber-level access and above, to change the email, password, and other details of any user, including Administrator users.