iOS 9.3.1 (build 13E238) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2016-03-31T16:55:05Z. The update package is 1.08 GB. This is a delta (partial) update that requires 8.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 07eea2a8408b6bcb1fc757d3878b4f46c20f8a7d.zip.