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Product: InterWorx Web Control Panel
Vendor: InterWorx LLC
Tested Version: 5.0.12 build 569
Vulnerability Type: Cross-Site Scripting [CWE-79]
CVE Reference: CVE-2014-2035
Risk Level: Medium
CVSSv2 Base Score: 6.4 (AV:N/AC:L/Au:N/C:P/I:P/A:N)
Solution Status: Fixed in Version 5.0.13 build 574
Discovered and Provided: Eric Flokstra (www.itsec.nl)

About the Vendor

The InterWorx Hosting Control Panel is a web hosting and linux server
management system that provides tools for server administrators to
command their servers and for end users to oversee the operations of
their website.

Advisory Details:

Reflected cross-site scripting (XSS) vulnerability in the InterWorx
Web Control Panel.

The application uses XMLHttpRequests to post messages to the web
server. However, insufficient output encoding is performed enabling
remote execution of arbitrary scripting code in the target's web
browser. By changing the request method from POST to GET the following
URL could be used as proof of concept:

http://demo.interworx.com:2080/xhr.php?i={%22r%22%3a%22Form_InputValidator%22%2c%22i%22%3a{%22form%22%3a%22Form_NW_Shell_ForbiddenUsers%22%2c%22ctrl%22%3a%22\%2fnodeworx\%2fshell%3Cimg%20src%3dx%20onerror%3dalert%28%27XSS%27%29%3E%22%2c%22input%22%3a%22forbidden_unix_users%22%2c%22value%22%3a%22moi%22%2c%22where_was_i%22%3a%22%2fnodeworx%2fshell%22}}

Vendor contact timeline:

18 Feb 2014: Vendor notification
18 Feb 2014: Vulnerability confirmation
19 Feb 2014: Issue patched
20 Feb 2014: Public disclosure

Solution:

Upgrade to the latest version (5.0.13 build 574) of InterWorx Web Control Panel.

References:

[1] InterWorx Changelog - http://www.interworx.com/developers/changelog/
[2] Common Vulnerabilities and Exposures (CVE) - http://cve.mitre.org
[3] Common Weakness Enumeration (CWE) - http://cwe.mitre.org