Modern Events Calendar <= 7.12.1 - Authenticated (Subscriber+) Server Side Request Forgery

The Modern Events Calendar plugin for WordPress is vulnerable to Server-Side Request Forgery in all versions up to, and including, 7.12.1 via the 'mec_fes_form' AJAX function. This makes it possible for authenticated attackers, with Subscriber-level access and above, to make web requests to arbitrary locations originating from the web application and can be used to query and modify information from internal services.