The WP Rocket plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to, and including, 3.21.0.1. This is due to insufficient input sanitization and output escaping of user-supplied data via the rocket_beacon AJAX endpoint. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
CWE-79