The flaw lies in the way that the PayPal authentication flow works with the service’s mobile apps for iOS and Android. It’s on the server side, and researchers at Duo Security developed a proof-of-concept app that can exploit the vulnerability. PayPal has been aware of the issue since March and has implemented a workaround, but isn’t planning a full patch until the end of July.
Using the app they built to exploit the vulnerability, the researchers were able to transfer money from a 2FA-protected account with just the username and password. In an interview, Lanier said there were any number of ways to accomplish that task, none of which is very complicated.
“There are plenty of cases of PayPal passwords being compromised in giant database dumps, and there’s also been a giant rise in PayPal related phishing,” he said. “That approach is already being used. People have long been and are continuing to do so. The whole two factor thing was supposed to make you feel all warm and fuzzy if your password is compromised. I’d probably use one of these techniques that are pretty darn efficient or maybe iterate through the public dumps of passwords.”"