this was flagged by @Daimona on the review of https://gerrit.wikimedia.org/r/c/mediawiki/skins/CologneBlue/+/637771/2/includes/CologneBlueTemplate.php#395
Set the qbfind message to:
"<script>alert(0);</script>Findz",`
Cologne blue will alert 0.
This happens in current master and was only flagged(noticing) during adjustments to the code.