A weakness, two security issues and some vulnerabilities have been reported in MediaWiki, which can be exploited by malicious users to disclose potentially sensitive information and by malicious people to conduct cross-site scripting, script insertion, and cross-site request forgery attacks and bypass certain security restrictions.

1) Input passed via the comment of a "File:" tag to a non-existing file is not properly sanitised before being used. This can be exploited to insert arbitrary HTML and script code, which will be executed in a user's browser session in context of an affected site if malicious data is viewed.

2) Input passed via the "uselang" parameter to index.php is not properly sanitised before being returned to the user via certain gadgets. This can be exploited to execute arbitrary HTML and script code in a user's browser session in context of an affected site.

3) The application allows users to perform certain actions HTTP requests without performing proper validity checks to verify the requests. This can be exploited to perform certain unspecified actions when a logged-in user visits a specially crafted web page.

4) An error when handling IP address blocking of the GlobalBlocking extension can be exploited to bypass the blocking mechanism and e.g. create an account from a blocked address.

5) The application stores user credentials used via external authentication plugins (e.g. LDAP extension) additionally in the local database and can potentially be exploited to bypass the strict function of an authentication plugin and log-in by using an old password.

6) An error when handling the blocking of users can be exploited to disclose the block reason via another block attempt.

Successful exploitation of this weakness requires administrative privileges.

The weakness, security issues, and vulnerabilities are reported in versions prior to 1.18.5 and prior to 1.19.2.

Solution
Update to version 1.18.5 or 1.19.2 and apply the vendor workaround in case only external authentication is used (please see the vendor's advisory for details).

Provided and/or discovered by
1) Writ Keeper in a MediaWiki bug report.
2) Fomafix in a MediaWiki bug report.
3, 4, 5, and 6) Reported by the vendor.

Changelog
Further details available to Secunia VIM customers

Original Advisory
MediaWiki:
http://lists.wikimedia.org/pipermail/mediawiki-announce/2012-August/000119.html
https://www.mediawiki.org/wiki/Release_notes/1.18
https://www.mediawiki.org/wiki/Release_notes/1.19
https://bugzilla.wikimedia.org/show_bug.cgi?id=37587
https://bugzilla.wikimedia.org/show_bug.cgi?id=39180
https://bugzilla.wikimedia.org/show_bug.cgi?id=39184
https://bugzilla.wikimedia.org/show_bug.cgi?id=39700
https://bugzilla.wikimedia.org/show_bug.cgi?id=39823
https://bugzilla.wikimedia.org/show_bug.cgi?id=39824

Deep Links
Links available to Secunia VIM customers