Revision Manager TMC <= 2.8.19 - Missing Authorization to Authenticated (Subscriber+) Arbitrary Email Sending

The Revision Manager TMC plugin for WordPress is vulnerable to unauthorized arbitrary email sending due to a missing capability check on the _a_ajaxQuickEmailTestCallback() function in all versions up to, and including, 2.8.19. This makes it possible for authenticated attackers, with subscriber-level access and above, to send emails with arbitrary content to any individual through the vulnerable web server.