An issue was discovered in the Widgets extension for MediaWiki through 1.35.1. Any user with the ability to edit pages within the Widgets namespace could call any static function within any class (defined within PHP or MediaWiki) via a crafted HTML comment, related to a Smarty template. For example, a person in the Widget Editors group could use \MediaWiki\Shell\Shell::command within a comment.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-35625
• https://gerrit.wikimedia.org/r/q/Ic899a8b15bc510e61cdacb5c024af2d226a2dbeb
• https://phabricator.wikimedia.org/T269718