Cross-site scripting (XSS) vulnerability in the Parser::replaceInternalLinks2 method in MediaWiki before 1.23.15, 1.26.x before 1.26.4, and 1.27.x before 1.27.1 allows remote attackers to inject arbitrary web script or HTML via vectors involving replacement of percent encoding in unclosed internal links.
MediaWiki before 1.23.15, 1.26.x before 1.26.4, and 1.27.x before 1.27.1 does not generate head items in the context of a given title, which allows remote attackers to obtain sensitive information via a parse action to api.php.
MediaWiki before 1.23.15, 1.26.x before 1.26.4, and 1.27.x before 1.27.1 allows remote authenticated users with undelete permissions to bypass intended suppressrevision and deleterevision restrictions and remove the revision deletion status of arbitrary file revisions by using Special:Undelete.