A iOS 8.1 Bug about UINavigationController
When a UINavigationController's viewControllers(more than 3) return different values in
prefersStatusBarHidden, the navigationBar will mess up when poping.
Can be 100% recreated on iOS 8.1 simulator, can happen on iOS 8.1 device but not sure if it can be 100% recreated. Fixed on iOS 8.2, won't happen on iOS7. Didn't test on iOS 8.0.
Code of blog post on longtimenoc