Guest Support <= 1.2.3 - Unauthenticated User Email Disclosure in guest_support_handler AJAX Endpoint

The Guest Support plugin for WordPress is vulnerable to User Email Disclosure in versions up to, and including, 1.2.3. This is due to the plugin exposing a public AJAX endpoint that allows anyone to search for and retrieve user email addresses without any authentication or capability checks. This makes it possible for unauthenticated attackers to enumerate user accounts and extract email addresses via the guest_support_handler=ajax endpoint with the request=get_users parameter.