In MediaWiki before 1.35.1, the combination of Html::rawElement and Message::text leads to XSS because the definition of MediaWiki:recentchanges-legend-watchlistexpiry can be changed onwiki so that the output is raw HTML.
{ "urgency": "not yet assigned" }
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2020-35474.json"