Uh...this is probably a hardware flaw.

Without recalling all iPhones prior to the Secure Enclave, I'm not exactly sure how they would 'fix it'.

There is no reason to assume that apple is either aware of the bug, or that they assisted the FBI in breaking the phone.

It is not only common, but NORMAL for hackers to have unknown exploits before the vendor is aware of them. Where do you think 0-days come from? In fact, there is an annual competition to break these devices with previously unknown attacks at CanSecWest.

Example: http://9to5mac.com/2014/11/13/iphone-5s-samsung-galaxy-s5-ne...

How would Apple know that _a_ vulnerability they know of is _the_ vulnerability that the FBI used, and that the FBI does not want to talk about, other than that it gave it access to one iPhone 5?

What makes you assume that?

Why would you assume that?

It's more likely that Apple did the work for them and they are both hiding it.