Apple has released iOS 11.3.1 and a macOS High Sierra 10.13.4 security update.
According to Apple iOS 11.3.1 improves the security of your iPhone or iPad and addresses an issue where touch input was unresponsive on some iPhone 8 devices because they were serviced with non-genuine replacement displays. iOS 11.3.1 can be downloaded for free over-the-air in the Settings app. Go to Settings –> General –> Software Update.
Apple says the security update for macOS High Sierra 10.13.4 improves security. The upgrade can be downloaded at the Mac App Store or via the Software Update function in the Mac App Store on Macs that are already running macOS High Sierra.