iOS 11.3 (build 15E5216a) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2018-03-16T17:05:17Z. The update package is 52.91 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: fd20430e5940ee497ceebe622b41a19153ee7d25.zip.