Call Now Button <= 1.5.3 - Missing Authorization to Authenticated (Subscriber+) Limited Plugin Settings Update

The Call Now Button – The #1 Click to Call Button for WordPress plugin for WordPress is vulnerable to unauthorized modification of data due to a missing capability check on the activate function in all versions up to, and including, 1.5.3. This makes it possible for authenticated attackers, with Subscriber-level access and above, to link the plugin to their nowbuttons.com account and add malicious buttons to the site. The vulnerability is only exploitable on fresh installs where the plugin has not been previously configured with an API key.