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.
{
"severity": "Medium",
"cpes": [
"cpe:2.3:a:mediawiki:mediawiki:*:*:*:*:*:*:*:*"
]
}