Information
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Advisory by Netsparker (now Invicti)
Name: Cross-site scripting vulnerability in Invision Power Board version 3.2.3
Software: Invision Power Board version 3.2.3
Vendor Homepage: http://www.invisionpower.com
Vulnerability Type: Cross-site scripting
Severity: High
Researcher: Vasil A.
Advisory Reference: NS-12-005

Description
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Invision Power Board (abbreviated IPB, IP.Board, or IP Board) is an Internet forum software produced by Invision Power Services, Inc. It is written in PHP and primarily uses MySQL as a database management system, although support for other database engines is available.

While Invision Power Board is a commercially sold product, there is a large modding community and many of these modifications are free. In addition, many groups offer the download or design of free and paid skins.

Details
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IP Board is affected by a cross-site scripting vulnerability in version 3.2.3.

Example PoC url is as follows :
http://example.com/forums/index.php?showforum=53"><script>with(document)alert(cookie)</script>

Additional notes:
1.If a forum contain sub-forums this vulnerability don't exist.

2.Most of boards uses "Friendly Url style",but the attack can be performed  by using "legacy URL style" in the query,e.g :

http://example.com/forum/index.php?showforum=2"><script>alert(/xss/.source)</script>

instead:

http://example.com/forum/index.php?/forum/2-example/

You can read the full article about Cross-site Scripting vulnerability from here:

Solution
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The vendor issued a patch for this vulnerability. Please see the references.

Advisory Timeline
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10/03/2012 - First contact: Sent the vulnerability details
12/03/2012 - Second contact: Ask for a patch
14/03/2012 - Vulnerability Fixed
29/03/2012 - Vulnerability Released

Credits
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It has been discovered on testing of Invicti.

References
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About Invicti
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Invicti Security is transforming the way web applications are secured. Invicti empowers organizations in every industry to scale their overall security operations, make the best use of their security resources, and engage developers in helping to improve their overall security posture.