Re: XSS

[Matthew Miller <mmiller () atstake com>]

John-

Two things....

First, there are really two types of XSS.  Persistent, where the 
injected code is stored within the web application, such as in 
distribution lists, databases, etc..., Transaction based, requiring a 
user to perform an action in order to be affected, such as click on a 
link, view a page with malicious script in it, etc...  Therefore, any 
site that is accepting any form of user input is potentially 
vulnerable...though the risk of persistent XSS exceeds the risk of 
transaction based XSS in most cases.

Second, XSS is not only used to grab a users session ID.  An attacker 
could inject code into the page to redirect the user or modify 
presentation of content.  Imagine an corporate site where you could 
add/modify a press release or news items, could you impact the 
companies stock price or lessen consumer confidence?  Imagine a 
pharmaceutical site where you could modify dosage for medication, could 
you get someone to overdose?

mm
--
Matthew P. Miller
www.atstake.com

On Tuesday, December 10, 2002, at 11:35 AM, John Madden wrote:

> Hi All,
>
> Thanks to everyone for their responses.
>
> Maybe i did not express myself well enough. What I
> wanted to know is if a site is vulnerable to XSS but
> doesn't allow any write operation, any postings for
> other users to actualy use the malicious URL, can it
> be used for something else ? The reason i'm asking is
> that the company I work for is vulnerable but doesn't
> allow any kind of user input (basicly it's just
> information site) We have to weight the treath vs
> cost, if nothing can be done with the XSS (no to say
> that they will never allow any user input...) then it
> will have a lower priority in the recommendations and
> if to fix all the web pages cost mucho $$$$ then we
> have to consider that as well.
>
> Any ideas ?
>
> --- Kevin Spett <kspett () spidynamics com> wrote:
> > We've got an XSS paper that describes a real attack
> > in technical detail.
> > The scenario it uses is a bank login page that uses
> > client-supplied data for
> > a login-failed error message.
> >
> > http://www.spidynamics.com/mktg/xss
> >
> >
> > I hope it helps.
> >
> >
> >
> > Kevin Spett
> > SPI Labs
> > http://www.spidynamics.com/
> >
> > ----- Original Message -----
> > From: "John Madden" <chiwawa999 () yahoo com>
> > To: <webappsec () securityfocus com>
> > Sent: Tuesday, December 10, 2002 9:38 AM
> > Subject: XSS
> >
> >
> > > Hello all,
> > >
> > > Being new to XSS and seing alot of messages in the
> > > last couple weeks on the subject got me
> > wondering...
> > > What is the real vulnerability if the site in
> > > questions is vulnerable to XSS but does not let
> > you
> > > write any malicious scripts on the system, like
> > > message board, forums etc... ? Can anything be
> > done to
> > > exploit XSS if the above scenario occurs ? I know
> > it
> > > depends on the web server, packages installed
> > etc...
> > > I'm asking in generaly is it possible ?
> > >
> > > You can do the document.cookie and view your
> > > cookie, that migth give a hint on the structure
> > but...
> > > or redirect yourself to another web site :) etc...
> > >
> > > I've read the document on XSS by David Endler
> > > http://www.idefense.com/papers.html but still have
> > > some questions.
> > >
> > > If possible, can the XSS guru's on the list shed
> > some
> > > light on the subject.
> > >
> > > Thanks for your time,
> > >
> > > Cheers
> > >
> > >
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