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.

ApiParse 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 bypass intended per-title read restrictions via a parse action to api.php.

Cross-site scripting (XSS) vulnerability in the CSS user subpage preview feature 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 the edit box in Special:MyPage/common.css.

MediaWiki before 1.23.15, 1.26.x before 1.26.4, and 1.27.x before 1.27.1, when $wgBlockDisablesLogin is true, might allow remote attackers to obtain sensitive information by leveraging failure to terminate sessions when a user account is blocked.

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.

MediaWiki before 1.23.12, 1.24.x before 1.24.5, 1.25.x before 1.25.4, and 1.26.x before 1.26.1 do not properly normalize IP addresses containing zero-padded octets, which might allow remote attackers to bypass intended access restrictions by using an IP address that was not supposed to have been allowed.

The (1) Special:MyPage, (2) Special:MyTalk, (3) Special:MyContributions, (4) Special:MyUploads, and (5) Special:AllMyUploads pages in MediaWiki before 1.23.12, 1.24.x before 1.24.5, 1.25.x before 1.25.4, and 1.26.x before 1.26.1 allow remote attackers to obtain sensitive user login information via crafted links combined with page view statistics.

MediaWiki before 1.23.12, 1.24.x before 1.24.5, 1.25.x before 1.25.4, and 1.26.x before 1.26.1 do not properly sanitize parameters when calling the cURL library, which allows remote attackers to read arbitrary files via an @ (at sign) character in unspecified POST array parameters.

The User::matchEditToken function in includes/User.php in MediaWiki before 1.23.12, 1.24.x before 1.24.5, 1.25.x before 1.25.4, and 1.26.x before 1.26.1 does not perform token comparison in constant time before determining if a debugging message should be logged, which allows remote attackers to guess the edit token and bypass CSRF protection via a timing attack, a different vulnerability than CVE-2015-8623.