The Relevanssi Premium plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the '_rt' parameter in all versions up to, and including, 2.31.4 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This requires the click-tracking and logging feature to be activated in the plugin settings, and exploitation is trivially accessible to unauthenticated users because a valid _rt_nonce is publicly emitted on every search-results page.