Advisory ID: HTB23109
Product: Phorum
Vendor: Phorum Team
Vulnerable Version(s): 5.2.18 and probably prior
Tested Version: 5.2.18
Vendor Notification: August 8, 2012 
Public Disclosure: August 29, 2012 
Vulnerability Type: Cross-Site Scripting [CWE-79]
CVE Reference: CVE-2012-4234
CVSSv2 Base Score: 4.3 (AV:N/AC:M/Au:N/C:N/I:P/A:N)
Solution Status: Fixed by Vendor
Risk Level: Medium 
Discovered and Provided: High-Tech Bridge Security Research Lab ( https://www.htbridge.com/advisory/ ) 

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Advisory Details:

High-Tech Bridge Security Research Lab discovered vulnerability in Phorum, which can be exploited to perform Cross-Site Scripting (XSS) attacks.

1) Cross-Site Scripting (XSS) in Phorum: CVE-2012-4234

Input passed via the "group" GET parameter to /control.php is not properly sanitised before being returned to the user.
This can be exploited to execute arbitrary HTML and script code in user's browser session in context of an affected website.

The following PoC demonstrates the vulnerability:

http://[host]/control.php?0,panel=groupmod,group=%22%3E%3Cscript%3Ealert%28document.cookie%29;%3C/script%3E

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Solution:

Upgrade to Phorum 5.2.19

More Information:
http://www.phorum.org/phorum5/read.php?64,151943

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References:

[1] High-Tech Bridge Advisory HTB23109 - https://www.htbridge.com/advisory/HTB23109 - Cross-Site Scripting (XSS) in Phorum.
[2] Phorum - http://www.phorum.org - Started in 1998, Phorum was the original PHP and MySQL based Open Source forum software.
[3] Common Vulnerabilities and Exposures (CVE) - http://cve.mitre.org/ - international in scope and free for public use, CVE® is a dictionary of publicly known information security vulnerabilities and exposures.
[4] Common Weakness Enumeration (CWE) - http://cwe.mitre.org - targeted to developers and security practitioners, CWE is a formal list of software weakness types. 

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Disclaimer: The information provided in this Advisory is provided "as is" and without any warranty of any kind. Details of this Advisory may be updated in order to provide as accurate information as possible. The latest version of the Advisory is available on web page [1] in the References.