The Responsive Video Embedder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'rem_video' shortcode in versions up to, and including, 0.1. This is due to insufficient input sanitization and output escaping on user supplied attributes (notably 'id' and 'list') in the video_shortcode() function, which are concatenated directly into an HTML iframe's src attribute without 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.