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Message-id: <459E9611.7050103@gmail.com>
Date: Fri, 05 Jan 2007 20:16:49 +0200
From: Amit Klein <aksecurity@...il.com>
To: RSnake <rsnake@...cking.com>
Cc: bugtraq@...urityfocus.com,
Web Security <websecurity@...appsec.org>
Subject: Re: [WEB SECURITY] Universal XSS with PDF files: highly dangerous
RSnake wrote:
>> 2. While thinking more about this solution, I observed that if the
>> attacker can have an "agent" sharing the same IP address with the
>> victim (by agent I mean an entity that can communicate with the
>> target web site and read back its response data), then the algorithms
>> I suggested will not be effective. Note that an attacker can share IP
>> address with the victim when both share a forward proxy (e.g. some
>> universities and ISPs), or when the attacker and victim share the
>> same machine (multi-user environment). Still, that narrows down the
>> attack surface significantly.
>
> It should be noted that this isn't as rare as just a few universities
> and ISPs. This also happens in lots of corporate networks (rogue user
> on the internal network), it happens with lots of internet cafe's, it
> happens with AOL (~5MM users) and it happens with TOR users. So while,
> yes, I agree it is better than nothing it is hardly a rock solid
> solution for anyone on a shared IP.
>
The point is - someone with shared IP is vulnerable ONLY to an attacker
with the same IP. Which makes attacks much less generic and much more
painful. Rock solid it ain't, but I think it's a pretty good band-aid
until all (hmmm...) clients upgrade to Acrobat Reader 8.0.
-Amit
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