The Relevanssi – A Better Search plugin for WordPress is vulnerable to unauthorized modification of data due to a missing capability check on the relevanssi_update_counts() function in all versions up to, and including, 4.22.1. This makes it possible for unauthenticated attackers to execute expensive queries on the application that could lead into DOS.
https://plugins.trac.wordpress.org/changeset/3064304/relevanssi/tags/4.22.2/lib/admin-ajax.php
https://plugins.trac.wordpress.org/browser/relevanssi/trunk/lib/admin-ajax.php#L443