iOS 11.3 (build 15E216) is an official Apple over-the-air update for the iPhone 5s (Global), released on 2018-03-29T17:11:58Z. The update package is 1.3 GB. This is a delta (partial) update that requires 10.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 0644b86796eb62ed4ecb1e31891805cc6aac19cc.zip.