Summary With $wgEmbedVideoRequireConsent disabled (not the default), the urls for videos are passed into an iframe src attribute without sanitization. When given a malformed url or id, the src attribute can be escaped via double quotes, allowing for html/javascript injection.

Details The iframe assembled here adds the url from getUrl() as the src without sanitization. The id regex for the archiveorg service and the url regexes for the wistia and sharepoint services allow for double quotes to be introduced.

PoC Using double quotes, the src attribute can be escaped. <embedvideo service="archiveorg" id='a" onmouseover="alert(document.domain)" data-x="'></embedvideo>

Impact When $wgEmbedVideoRequireConsent = false, any user able to edit a page can inject arbitrary JavaScript into an HTML event handler attribute (e.g. onfocus) via parameter. It requires no interaction (autofires via autofocus) and executes in the wiki origin for every visitor to the page.