MediaWiki before 1.15.3, and 1.6.x before 1.16.0beta2, does not properly handle a correctly authenticated but unintended login attempt, which makes it easier for remote authenticated users to conduct phishing attacks by arranging for a victim to login to the attacker's account and then execute a crafted user script, related to a "login CSRF" issue.

thumb.php in MediaWiki before 1.15.2, when used with access-restriction mechanisms such as img_auth.php, does not check user permissions before providing scaled images, which allows remote attackers to bypass intended access restrictions and read private images via unspecified manipulations.

MediaWiki before 1.15.2 does not prevent wiki editors from linking to images from other web sites in wiki pages, which allows editors to obtain IP addresses and other information of wiki users by adding a link to an image on an attacker-controlled web site, aka "CSS validation issue."