JoomSport <= 5.7.8 - Authenticated (Subscriber+) Missing Authorization to Arbitrary Group Creation/Modification via season_groupedit AJAX action

The JoomSport – for Sports: Team & League, Football, Hockey & more plugin for WordPress is vulnerable to authorization bypass in all versions up to, and including, 5.7.8. This is due to the plugin not properly verifying that a user is authorized to perform an action. This makes it possible for authenticated attackers, with subscriber-level access and above, to create arbitrary season groups or modify existing group names, participants, and round-type options. Exploitation requires obtaining the joomsportajaxnonce, which is exposed on frontend pages that render a JoomSport shortcode.