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Date: Fri, 4 Oct 2013 10:20:06 +0200
From: Igor Sverkos <>
Subject: Re: A note on cookie based sessions


Kurt Seifried wrote:
>> I don't think this really is a vulnerability is it? I mean it's
>> basically how the internet works. The only difference between a
>> cooke backed session and a regular session is that there's no
>> server side session to destroy. At least in Django's case, It's not
>> a permanent session though, they are only good for a limited amount
>> of time before the signature on the cookie expires.
>> If you have access to the session cookie you've already won the
>> game, you've gotten an XSS or MITM and can do much worse then a
>> session cookie.
> [...]
> The concern is people using public terminals, cookie stealing attacks,
> XSS in the website you're using, etc allowing an attacker to snag your
> cookie and use it post "log out".

I am not sure about the intention of your mail.

But if you want to warn people, don't forget people using applications
like vBulletin: They don't use SSL and if you got the cookies, you are in.

Teaching these people to use the logout button won't fix the problem:
This will only destroy the cookie on the user's browser. But if you have
sniffed the cookies, you can restore the cookies and you are back in,
because the cookies are always the same (as long as you don't change your
For me this is a bigger problem, because people think "Hey I logged out,
I am safe" but they aren't and because they don't know they will wonder...

I think I don't have to mention that it is really easy to get these
cookies using technics FireSheeps & Co. demonstrated years ago.

And in times where people using every available network to access
internet, because they don't know better/don't care about MITM, it isn't
really hard to get cookies like that. Just go into a coffee shop with your
UMTS hotspot, name your network "free-internet" and watch.

PS: To be fair: To access vBulletin's {Admin,Mod}CP you will be prompted
for the password again. But many boards are running modifications which
allows staff to use many functions from the frontend (which will bypass
this protection).


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