Security researchers demonstrated that a Wrong oAuth 2.0 implementation allows a remote simple hack that exposes more than 1 Billion Android App Accounts. Attackers can use the technique to sign into any victims mobile app account without any knowledge of the legitimate user. Over a Billion different mobile app accounts are at risk of being hijacked with their attack. The researchers did not perform any test on iOS devices, but they believed that the attack would work also on Apple apps. Over 2.4 Billion downloads are vulnerable to this attack.”]
Source: http://securityaffairs.co/wordpress/53081/hacking/oauth-2-0-attack.html