The iPhone’s most mysterious and dangerous bug is tied to Touch ID tampering and unauthorized repairs, at least according to Apple.

For months, some iPhone users have been running into a mysterious bug called “Error 53,” which can render some newer handsets unusable. Now, Apple has chimed in with an explanation.
With Error 53, some iPhone 6 and 6s users have found that their handsets no longer work after an iOS update. Stranger still, Apple’s support site barely documents the problem, lumping it in with other error codes that appear to be more easily resolved.
the only fix for Error 53 is to send the phone back to Apple and get a replacement.
But The Guardian has an update on the issue with official word from Apple on its cause. The company is blaming the problem on unauthorized third-party repairs, which can disrupt the unique pairing between the iPhone’s Touch ID fingerprint reader and the “secure enclave” that stores fingerprint data. Without this pairing, the risk is that someone could install a malicious Touch ID sensor and steal sensitive data, so Apple’s response is to shut everything down when the pairing fails.
“When an iPhone is serviced by an unauthorized repair provider, faulty screens or other invalid components that affect the Touch ID sensor could cause the check to fail if the pairing cannot be validated,” Apple’s spokeswoman said. “With a subsequent update or restore, additional security checks result in an ‘error 53’ being displayed.”
Why this matters: In lieu of any explanation from Apple, some observers have speculated that Error 53 is the company’s way of imposing a monopoly on repairs. Although Apple’s latest iPhones are fairly easy to fix, the unique Touch ID pairing process could jeopardize any do-it-yourself plans that involve the home button or its fingerprint reader. Apple’s statement suggests that this is the price users must pay to secure their fingerprints, which in turn can provide access to all kinds of sensitive data.
While Apple’s statement sheds some light on the company’s thinking, it doesn’t neatly answer every question about Error 53.
A spokeswoman for Apple told Money (get ready for a jargon overload): “We protect fingerprint data using a secure enclave, which is uniquely paired to the touch ID sensor. When iPhone is serviced by an authorized Apple service provider or Apple retail store for changes that affect the touch ID sensor, the pairing is re-validated. This check ensures the device and the iOS features related to touch ID remain secure. Without this unique pairing, a malicious touch ID sensor could be substituted, thereby gaining access to the secure enclave. When iOS detects that the pairing fails, touch ID, including Apple Pay, is disabled so the device remains secure.”
She adds: “When an iPhone is serviced by an unauthorized repair provider, faulty screens or other invalid components that affect the touch ID sensor could cause the check to fail if the pairing cannot be validated. With a subsequent update or restore, additional security checks result in an ‘error 53’ being displayed … If a customer encounters an unrecoverable error 53, we recommend contacting Apple support.”