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Home » Hacking News » acFreeProxy Cross-Site Scripting Vulnerability/Possible DoS

acFreeProxy Cross-Site Scripting Vulnerability/Possible DoS

by Nikola Strahija on November 25th, 2002 acFreeProxy (aka "acfp") is an HTTP/1.x proxy for Microsoft Windows environments. It offers caching, and several other features, and has a plug-in format designed for extensibility. A flaw in the product may allow attackers to execute content across domains.


The proxy server may generate an error message if given a host that it
cannot reach, or some other exceptional condition. The error page generated
during this process does not have any input validation, and is vulnerable to
cross-site scripting. This allows an attacker to inject code as *any site*
the victim can visit, because this problem is in the proxy, and not a
specific site.


This vulnerability is significantly more dangerous than any site-specific
flaw, as it can be exploited to read content from any domain, instead of the
limited scope of a typical cross-site scripting flaw, where the site that is
flawed is the only site that can be impacted.


If a vulnerable proxy is being run, script execution begins.

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