Apple released iOS 11.4.1. iOS 11.4.1 is mainly a bug fix release, with improved reliability of Find My AirPods, and syncing with mail, contacts, and notes with Exchange accounts.
iOS 11.4.1 also includes USB Restricted Mode, which was first introduced in the iOS 12 beta. USB Restricted Mode is designed to protect iPhones against USB devices used by law enforcement to crack your passcode, and works by disabling USB access after the phone has been locked for an hour.
USB Restricted Mode is enabled by default when you update to iOS 11.4.1. Toggle it on if you want USB accessories to be able to connect even if it’s been more than an hour since the iPhone or iPad was unlocked.