MMA Call Tracking <= 2.3.15 - Cross-Site Request Forgery to Plugin Settings Update

The MMA Call Tracking plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 2.3.15. This is due to missing nonce validation when saving plugin configuration on the `mma_call_tracking_menu` admin page. This makes it possible for unauthenticated attackers to modify call tracking configuration settings via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.