The YouTube Embed WordPress plugin before 5.2.2 does not validate escape or sanitise some of its shortcode attributes leading to Stored XSS issues by 1. using w h controls cc_lang color language start stop or style parameter of youtube shortcode 2. by using style class rel target width height or alt parameter of youtube_thumb shortcode or 3. by embedding a video whose title or description contains XSS payload (if API key is configured).