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FB Responsible Disclosure

Instagram iOS session hijack

Instagram makes API calls to non-HTTPS endpoints with session cookies in the request headers allowing full session hijack by a malicious actor.

Steps to reproduce (on Mac OS X):

  • Jump on an open or WEP encrypted wifi access point
  • Put your network interface into promiscuous mode filtering on
    sudo tcpdump -In -i en0 -s 2048 -A dst
  • Wait for someone to use the Instagram iOS app on the same network
  • Extract cookie request header from the resulting output
  • Use sessionid cookie parameter to make any api call as that user Even https endpoints like direct messages.
    curl -H 'User-Agent: Instagram 6.0.4 (iPhone6,2; iPhone OS 7_1_1; en_GB; en-GB) AppleWebKit/420+' \
     -H 'Cookie: sessionid=REDACTED' \`

This returns the user's direct message inbox as JSON

I was able to perform a session hijack on my own account on my laptop while someone else browsed instagram on my iPhone.

I was also able to:

  • take the cookie sniffed from the iOS app
  • go to as an unlogged in user.
  • set document.cookie = $COOKIE
  • navigate to a profile
  • see I'm logged in as that user

There is some screwy behaviour where '' gets into redirect loop, I will see if I can fix that. However going to '' works and shows me as logged in.

I think this attack is extremely severe because it allows full session hijack and is easily automated. I could go to the Apple Store tomorrow and reap thousands of accounts in one day, and then use them to post spam.


  • Use SSL everywhere
  • Revoke all logged-in sessions?

I'm adding another recomendation:

  • Sue me

@wodim I adhered to the FB responsible disclosure procedure. FB replied saying they're already aware of the issue and closed the ticket.


Can you crawl their contact list, or is that SSL-ed?


@wodim what would @stevegraham be sued for even if he didn't adhere to FB's responsible disclosure procedure? People might have frowned on releasing this information before disclosing it to Facebook, but AFAIK there is nothing here that Facebook could sue him for (and win the decision).


@jasiek The gist says the session is valid even on HTTPS endpoints.


That's a nice catch.


@jasiek once you have a cookie, any endpoint can be authenticated with the cookie, HTTPS or HTTP.


"Sue"? Maybe not. But in the good ol' US of A you can probably be prosecuted under this by anyone with a sufficiently large axe to grind.


Got the instasheep domain name if you want me to point it at a github repo.




As I read it works only on Mac though... right ?


@Mamugian Given that the Instagram user is connected via an unsecured connection (HTTP) to the API, any device capable of TCP dumping will be able to do this.


the tool is for what platform?? pc,mac,android???


@Mamugian could work on any unix/linux platform.


@jlopez1286 seriously? tcpdump. Didn't expect to see such question on this gist


Im not really experienced with packet sniffing and all this advanced networking stuff. But i was able to do the packet sniffing on an unsecured network using WireShark and get the session ID of the cookie headers. What do i have to do from here? I would be grateful if anyone could help.

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