Secunia

Some vulnerabilities and a weakness have been reported in MyBB, where some have an unknown impact, and others can be exploited by malicious people to conduct brute force or cross-site scripting attacks.

1) Input passed to the "url" parameter in moderation.php (when "action" is set to "removesubscriptions" and "ajax" to "1") is not properly sanitised before being returned to the user. This can be exploited to execute arbitrary HTML and script code in a user's browser session in context of an affected site.

Successful exploitation of this vulnerability requires that the victim has valid moderator or administrator credentials.

2) The problem is caused due to storing attachments with filenames based on the user ID and the timestamp, making them vulnerable to brute force attacks. This can be exploited to disclose sensitive information without valid user credentials.

3) Some vulnerabilities are caused due to unknown errors. No further information is currently available.

The vulnerabilities and the weakness are reported in all versions prior to 1.4.3 downloaded on 2008-10-29 or later.

Solution
Update to version 1.4.3 downloaded on 2008-10-29 or later.

Provided and/or discovered by
1, 2) Kellanved, NeoThermic, and Techie-Micheal
3) Reported by the vendor.

Changelog
Further details available in Customer Area

Original Advisory
MyBB:
http://community.mybboard.net/thread-39705.html

Kellanved, NeoThermic, and Techie-Micheal:
http://lists.grok.org.uk/pipermail/full-disclosure/2008-October/065280.html

Deep Links
Links available in Customer Area