Custom Related Posts <= 1.7.3 - Missing Authorization to Authenticated (Subscriber+) Private Post Search and Relation Updates

The Custom Related Posts plugin for WordPress is vulnerable to unauthorized access & modification of data due to a missing capability check on three AJAX actions in all versions up to, and including, 1.7.3. This makes it possible for authenticated attackers, with Subscriber-level access and above, to search posts and link/unlink relations.