iOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPhone 5s (Global), released on 2018-04-24T17:10:07Z. The update package is 31.5 MB. This is a delta (partial) update that requires 11.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 3ec6a97830e4941dcdf2b2aa27b5cfb2bde11659.zip.