About six weeks ago, a hole
in Paypal's two factor authentication and their mobile client was discovered. hypnosec (2231454)
wrote in with news of another trivial way to bypass Paypal's two-factor authentication
. A bug in a feature for eBay integration allows passing a GET parameter to completely bypass two-factor authentication, and you don't even need to be coming from eBay to use it. You still need the password, but additional protection is lost. From the article: eBay, in conjunction with Paypal, provide a service as to where you can link your eBay account to your Paypal account, and when you sell something on eBay, the fees automatically come out of your Paypal account. ... When you are redirected to the login page, the URL contains "=_integrated-registration." ... Once you're actually logged in, a cookie is set with your details, and you're redirected to a page to confirm the details of the process. And this is where the exploit lays. Now just load http://www.paypal.com/ , and you are logged in, and don't need to re-enter your login.
So, the actual bug itself is that the "=_integrated-registration" function does not check for a 2FA code, despite logging you into Paypal.
You could repeat the process using the same "=_integrated-registration" page unlimited times.