An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2. On Special:NewFiles, all the mediastatistics-header-* messages are output in HTML unescaped, leading to XSS.
https://www.debian.org/security/2021/dsa-4889
https://security.gentoo.org/glsa/202107-40