RE: A technique to mitigate cookie-stealing XSS attacks

From: Michael Howard (mikehowat_private)
Date: Thu Nov 07 2002 - 14:49:34 PST

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    We added a feature kinda like this to IE6, you can mark a <FRAME> with:
    
    <FRAME SECURITY=RESTRICTED ....>
    
    	<!-- blah blah -->
    
    </FRAME>
    
    And this will force all content into the IE Restricted Zone, which, by
    default will not allow much of anything to work.
    
    Cheers, Michael
    Secure Windows Initiative
    Writing Secure Code 
    http://www.microsoft.com/mspress/books/5612.asp
    
    
    -----Original Message-----
    From: Justin King [mailto:justinat_private] 
    Sent: Thursday, November 07, 2002 12:27 PM
    To: bugtraqat_private
    Cc: Michael Howard
    Subject: Re: A technique to mitigate cookie-stealing XSS attacks
    
    
    
    I would be very interested in major browsers supporting a <dead> tag
    with an optional parameter to be a hash of the data between the opening
    and closing dead tag. This tag would indicate that no "live" elements of
    HTML be supported (e.g., JavaScript, VBScript, embed, object).
    
    I know this has been suggested before. I would prefer to see RFC
    covering this, with support an implementation immediately following.
    
    -Justin
    
    ----- Original Message -----
    From: "Michael Howard" <mikehowat_private>
    To: <bugtraqat_private>
    Sent: Tuesday, November 05, 2002 13:44
    Subject: A technique to mitigate cookie-stealing XSS attacks
    
    
    During the Windows Security Push in Feb/Mar 2002, the Microsoft Internet
    Explorer team devised a method to reduce the risk of cookie-stealing
    attacks via XSS vulnerabilities.
    
    In a nutshell, if Internet Explorer 6.0 SP1 detects a cookie that has a
    trailing HttpOnly (case insensitive) it will return an empty string to
    the browser when accessed from script, such as by using document.cookie.
    
    
    Obviously, the server must add this option to all outgoing cookies.
    
    Note, this does _not fix_ XSS bugs in server code; it only helps reduce
    the potential damage from cookie disclosure threats. Nothing more. Think
    of it as a very small insurance policy!
    
    A full write-up outlining the HttpOnly flag, as well as source code to
    set this option, is at
    http://msdn.microsoft.com/library/en-us/dncode/html/secure10102002.asp.
    
    Cheers, Michael Howard
    Secure Windows Initiative
    Microsoft Corp.
    
    Writing Secure Code http://www.microsoft.com/mspress/books/5612.asp
    



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