Re: XSS Questions

From: Martin Wasson (martin_wassonat_private)
Date: Tue Dec 10 2002 - 10:24:40 PST

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    John,
    The vulnerability is in that the server does not sanitize data it sends to
    the client.  Sanitizing input not withstanding, a server must sanitize it's
    output to avoid this lawlessness.  Otherwise an eville haxor can get your
    site to send your customer a link to his site, wherein your customer's box
    can unwittingly execute malicious code, and BOOM !! therefore divulge lots
    of sensetive data., e.g.  username, password, SSN, home address, etc.  Get
    it?  BOOM !!....John Madden.....  I kill me.  So accepting user input
    doesn't matter in this situation...it's the ouput, bro.
    
    
    Marty Wasson
    Web Security Admin
    Mastercard International
    martin_wassonat_private
    
    
                                                                                                                                           
                          John Madden                                                                                                      
                          <chiwawa999@yahoo        To:       pen-testat_private                                                    
                          .com>                    cc:       (bcc: Martin Wasson/STL/MASTERCARD)                                           
                                                   Subject:  XSS Questions                                                                 
                          12/07/02 08:36 AM                                                                                                
                                                                                                                                           
                                                                                                                                           
    
    
    
    
    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 ?
    
    Great 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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