In keeping with tradition, the Apple guys just stop signing iOS 11.3, the third major update of iOS 11, so that we can only restore our device to iOS 11.3.1 in case our device offers any problem of operation or performance, so if you are a jailbreak user, treat your iPhone the best that you can.
Stop signing older versions of iOS, once a new version is released, is Apple's way of ensuring that all users are always updated to the latest version of iOS that the company currently offers users, a version that in theory protects against any security problem that has been detected up to that moment.
iOS 11.3.1 in addition to solving small operating bugs, it solved the problem that some devices presented when they changed the screen of their devices in an unauthorized establishment, so I can't quite understand what Apple's rush is to stop signing iOS 11.3, a version that brought us a large number of new features, although not all of those that had been available in the beta process, such as synchronization Messages with iCloud or AirPlay 2.
Currently, the guys from Cupertino are working on the next big iOS update, an update that will lead to number 11.4. This update is It should offer the function that allows us to synchronize messages through iCloud in addition to activating AirPlay 2, a function that allows us to play content independently on each of the speakers or Apple TV that we have distributed throughout our home from a single device.
The release of the final version of iOS 11.4, it is likely that be delayed until the end of this month of May or the beginning of June, date on which the World Conference for Developers (WWDC) will be held, in which the guys from Cupertino will present all the news that will come to Apple's mobile and desktop products from the month of September.