RE: (Fwd) MSIEv6 % encoding causes a problem again

From: Thor Larholm (Thorat_private)
Date: Thu Sep 05 2002 - 02:18:42 PDT

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    > From: Nick FitzGerald [mailto:nick@virus-l.demon.co.uk]
    > Hi Thor,
    > Doesn't the following have similar implications to the issue in your 
    > TL#002 advisory??
    
    Hi Nick,
    
    close but no cigar - yet. In its current state, this % encoding issue cannot
    escape protocol boundaries, which means that it cannot go from the Internet
    Zone to the My Computer Zone and execute commands or read local files.
    
    It can, however, do arbitrary cross domain scripting on any site in its
    current protocol, which means that you can steal cookies and read/change
    arbitrary content from foreign sites. If you e.g. have an HTTPS site
    yourself, you can read/change the content for any other HTTPS site dispalyed
    to the user - change the login form actions, read the users bank accounts,
    etc.
    
    The issue is not so much with escaped versions of / or \, but with escaping
    of characters in itself. When actually retrieving the content, IE looks at
    the escaped version of your URI and fetches your malicious code from
    brinkster.com (escaping the yahoo.com part makes it part of Basic
    Authentication). When it later needs to check cross domain security settings
    and see whether the 2 windows may communicate, it looks at the unescaped
    version of your URI - which by now is a reference to yahoo.com instead of
    brinkster.com, with the Basich Authentication being part of the filename.
    
    
    Regards
    Thor
    



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