MediaElement.js – HTML5 Video & Audio Player <= 4.2.8 - Contributor+ Stored XSS via Shortcode

The MediaElement.js WordPress plugin through 4.2.8 does not validate and escape some of its shortcode attributes before outputting them back in the page, which could allow users with a role as low as contributor to perform Stored Cross-Site Scripting attacks which could be used against high-privilege users such as admins.