If you've had the Touch ID fingerprint reader on your iPhone repaired through unofficial channels, it could be at risk of being bricked if it's upgraded to iOS 9.
Apple responds: 'Error 53' is not a bug, it's a feature
The Guardian has a story of a freelance photographer, Antonio Olmos, who broke his iPhone while working in Macedonia. Because of the lack of an official Apple repair center, Olmos had it replaced by an unofficial third-party. Later his iPhone was offered an iOS upgrade that failed to complete and left him with a bricked handset showing error 53.
Apple says there is nothing that can be done short of buying a new iPhone.
"The whole thing is extraordinary," said Olmos. "How can a company deliberately make their own products useless with an upgrade and not warn their own customers about it?"
Olmos isn't the only person affected by this. A quick Google search unearths a lot of people who've been left with a bricked iPhone.
The issue is that if the Touch ID sensor is replaced - of the ribbon cable it is attached to - the new parts need to be paired with the iPhone. And the rub is that only be carried out by an authorized repair center. iOS 9 appears to check for this pairing, and if it has not been carried out, it bricks the iPhone without warning.
Since the Touch ID sensor is central to the security of the iPhone and Apple Pay, it makes sense that it incorporates anti-tampering security features, but that's little comfort to those who weren't expecting their device to be bricked by an update.
Bottom line, if you've had the Touch ID sensor replaced on an iPhone 6 or above by anyone other than an Apple authorized repair center, don't upgrade to iOS 9, because if you get hit by 'Error 53' then your iPhone is history.