WPGYM <= 67.1.0 - Missing Authorization to Authenticated (Subscriber+) Privilege Escalation

The WPGYM - Wordpress Gym Management System plugin for WordPress is vulnerable to privilege escalation due to a missing capability check on the MJ_gmgt_add_staff_member() function in all versions up to, and including, 67.1.0. This makes it possible for authenticated attackers, with subscriber-level access and above, to create new user accounts with the administrator role.