The Element Pack Elementor Addons (Header Footer, Template Library, Dynamic Grid & Carousel, Remote Arrows) plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘onclick_event’ parameter in all versions up to, and including, 5.6.11 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.