iOS 11.3 (build 15E5201e) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2018-03-05T18:14:00Z. The update package is 292.6 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: 44397bd4c013ff602d9a6e704cd5bc53f5ea285c.zip.