Earlier this week several iOS devices were getting hit with error 53 alerts on their devices. This error was caused by getting unofficial repairs done on your devices, most likely it was when the cable between TouchID and the rest of the device was replaced. It essentially rendered being able to use your device to a stand still, but Apple has issued a fix for it.
Customers affected by it can update or restore to a new version of iOS 9.2.1, this is not done through an over-the-air update though. To get this update your phone needs to be affected by this error and it has to be done through iTunes on your computer. This error is resulted in that the TouchID sensor has a lot of confidential information and it becomes an array of security concern. The result is with an unofficial module being installed, it results in bricking your iPhone or rendering it useless.
Apple has published a support page for the error 53 issue and it includes instructions on how to go about fixing it. You can see the support document with full instructions how to fix error 53 by clicking here.