An issue was discovered in MediaWiki before 1.31.12 and 1.32.x through 1.35.x before 1.35.2. ContentModelChange does not check if a user has correct permissions to create and set the content model of a nonexistent page.
lists.debian.org/debian-lts-announce/2021/05/msg00003.html
lists.debian.org/debian-lts-announce/2021/05/msg00006.html
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/26UJGHF7LJDOCQN6A3Z4PM7PYRKENJHE/
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2OMSV7B2TCFBOCICN3B4SMQP5HVRJQIT/
phabricator.wikimedia.org/T270988
security.gentoo.org/glsa/202107-40
www.debian.org/security/2021/dsa-4889