The plugin provides an Admin Search page that allows users with the editposts capability to run Relevanssi searches from the WordPress dashboard. The AJAX handler accepts a URL-encoded args parameter, parses it into a WPQuery, and then passes user-controlled taxonomy query data into Relevanssi's taxonomy restriction builder. The taxonomy value is sanitized as text but is not parameterized for SQL before being interpolated into a term taxonomy lookup query. This allows an authenticated contributor-level attacker to inject SQL through the Admin Search AJAX request and execute time-based blind SQL injection against the WordPress database.

Reflected XSS in Relevanssi Premium version 1.14.8 when using relevanssididyoumean() could allow unauthenticated attacker to do almost anything an admin can

WordPress plugin Relevanssi version 3.5.7.1 is vulnerable to stored XSS resulting in attacker being able to execute JavaScript on the affected site

In the process of testing the Relevanssi WordPress plugin before 4.23.1, a vulnerability was found that allows you to implement Stored XSS on behalf of the Contributor+ by embedding malicious script, which entails account takeover backdoor

The Relevanssi WordPress plugin before 4.22.0, Relevanssi Premium WordPress plugin before 2.25.0 allows any unauthenticated user to read draft and private posts via a crafted request