Who has not tried or sought ways to hack a Facebook account?
Yes, a critical failure in Facebook allows a hacker to hack multiple Facebook accounts.
Who has not tried or sought ways to hack a Facebook account?

But, it is only possible if you have authorized Facebook apps.
It will automatically change the ID into a username.
It simply requests a passcode to every user in the JSON file created earlier.

The efficacy of the bug I found relied on just that.

