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PR07-13 - Cross-site Scripting / HTML injection on F5 FirePass 4100 SSL VPN 'download_plugin.php3' server-side script

Vulnerability found:
19 June 2007
Severity level:
Jan Fry and Adrian Pastor of Procheckup Ltd
F5 Networks FirePass 4100 SSL VPN is vulnerable to XSS within the "backurl" parameter processed by the "download_plugin.php3" server-side script.
No authentication is required to exploit this vulnerability.


An attacker may be able to cause execution of malicious scripting code in the browser of a user who visits a specially-crafted URL to an F5 Firepass device, or visits a malicious page that makes a request to such URL. Such code would run within the security context of the target domain.
This type of attack can result in non-persistent defacement of the target site, or the redirection of confidential information (i.e. admin session IDs) to unauthorised third parties.
F5 Networks has confirmed the following versions to be vulnerable
FirePass versions 5.4 - 5.5.2

FirePass versions 6.0 - 6.0.1
Successfully tested on
Server environment-

F5 FirePass 4100

Client environment-

Microsoft Internet Explorer 7.0.5730.11



Proof of concept:

The payload is encoded in Base64, in the example it is
"><script src=""></script><a href="
which calls the malicious JavaScript code from a third-party URL ('' in this case), thus proving that scripting code can be run without restrictions of length or type of characters.

The payload is encoded in Base64, in the example it is
"><textarea>HTML injection test</textarea><a href="
which injects a 'textarea' box.
How to fix:
F5 Networks has issued SOL7498:
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