includes/CologneBlueTemplate.php in the CologneBlue skin for MediaWiki through 1.35 allows XSS via a qbfind message supplied by an administrator.
https://phabricator.wikimedia.org/T267278
https://gerrit.wikimedia.org/r/q/Ie798a4f16d0ac2a4871aefeb593d962966aeb6b0