GulfTech Security has discovered two vulnerabilities in YaBB, which can be exploited by malicious people to conduct cross-site scripting attacks and bypass certain security restrictions.

1) Input passed to the "board" parameter in "YaBB.pl" is not properly sanitised before being returned to the user. This can be exploited to execute arbitrary script code in a user's browser session in context of a vulnerable site.

Example:
http://[victim]/YaBB.pl?board=;action=imsend;to=[code]

2) Some administrative actions are performed just by accessing an URL. This can e.g. be exploited by malicious users by posting a message containing an image, which refers to an URL used for performing an administrative task, in a forum.

Successful exploitation invokes the action automatically when the administrator reads the forum posting.

Example (remove board):
http://[victim]/YaBB.pl?board=;action=modifycat;id=[cateogoryname];moda=Remove2

The vulnerabilities have been confirmed on YaBB 1 GOLD SP 1.3.2. Other versions may also be affected.

Solution
Edit the source code to ensure that input is properly sanitised.

Provided and/or discovered by
GulfTech Security

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