Mediawiki EmbedVideo Extension has stored XSS via malformed src url with $wgEmbedVideoRequireConsent disabled

A user who can edit a wiki page can store malicious JavaScript in an embedded video when $wgEmbedVideoRequireConsent is disabled, which is not the default. The script runs in the wiki's origin for every visitor to that page, without requiring interaction.

Check composer.lock for starcitizenwiki/embedvideo at version 4.0.0 or earlier. If present, check whether $wgEmbedVideoRequireConsent is set to false and whether pages use the archiveorg, wistia or sharepoint video services, whose ID or URL handling is identified as vulnerable. Version 4.1.0 contains the fix.

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.