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Re: Third party cookie handling in Opera can lead to potential compromises in Servers relying on redirection
From: George Capehart <gwc () acm org>
Date: Thu, 19 Aug 2004 18:28:29 -0400

On Tuesday 17 August 2004 04:34, Rohit Dube allegedly wrote:
 Opera's policy with respect to third party cookie makes it
vulnerable to session replay attacks. This was discovered 2 weeks
back. Opera's response to the same is attached. The issue and the
workaround are listed below.

Opera claims to be the fastest browser on earth and has the third
largest user base.

In case Opera privacy policy is set to refuse all third party
cookies, some servers (one is mail.yahoo.com) become susceptible to
session replay attacks. Reproduction steps, for mail.yahoo.com are:

<snip rest of discussion>

Seems to me that it's not Opera that is "at fault."  Browsers don't have 
sessions for which they need to maintain state.  Application servers 
do, though.  Shame on Yahoo for not maintaining state.  This is a 
significant problem for Yahoo and all other sites that use cookies but 
do not maintain their own idea of state and which don't protect 
themselves against session replay attacks.  Rule #1 of (especially 
distributed) applications:  DO NOT TRUST INPUT FROM A DOMAIN UNDER 
WHICH YOU HAVE NO CONTROL!!!!!!  This is just plain bad practice.


Best regards,

George Capehart
George W. Capehart

Key fingerprint:  3145 104D 9579 26DA DBC7  CDD0 9AE1 8C9C DD70 34EA

"With sufficient thrust, pigs fly just fine."  -- RFC 1925

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