Re: cross site scripint and post form

From: Jeremiah Grossman (jeremiah@whitehatsec.com)
Date: 10/12/01 

Message-ID: <3BC72309.C720F5DB@whitehatsec.com>
Date: Fri, 12 Oct 2001 10:06:17 -0700
From: Jeremiah Grossman <jeremiah@whitehatsec.com>
To: Carbone <carbonate@ifrance.com>
Subject: Re: cross site scripint and post form

You may be confusing some issues here. Cross-Site Scripting
occurs when third party or user supplied data is displayed within
a web environment without being properly handled. It make do
difference if the data came from a form, cookie, or even which
HTTP request method was used.

CSS is the simply the instance of HTML/JavaScript from an
outside source within a web environment, executing with the
same privileges and the hosting domain.

There currently are a few ways to combat CSS and its effects.
The most widely used appears to be search/replace in strings.

Hope this answers your question

Jeremiah-

Carbone wrote:

> Hello everybody
>
> A little question about cross site scripting. It's very easy to exploit this
> vulnerability with a "get" form : we just have to send at the victim a link
> like http://www.bla.com/foo.pl?blabla="attacker script". Then foo.pl output
> is the attacker script, and this script is executed on the victim navigator.
> But how to exploit this hole if the form of www.bla.com make a post request
> instead of a get request ? With a post request, we are not able to make the
> url like above.
>
> We see everywhere on the web that the solution against cross site scripting
> is to escape the special characters of the form. But maybe it's more easy to
> avoid GET forms ? Or maybe i miss something, and it's possible to exploit
> POST forms...
>
> What is your opinion about that ?
>
> Thank you

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