An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2. On ChangesList special pages such as Special:RecentChanges and Special:Watchlist, some of the rcfilters-filter-* label messages are output in HTML unescaped, leading to XSS.
https://www.debian.org/security/2021/dsa-4889
https://security.gentoo.org/glsa/202107-40