iOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPhone 7 (GSM), released on 2018-04-24T17:11:31Z. The update package is 1.4 GB. This is a delta (partial) update that requires 10.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: b160c92ac72ce78c02b2f4151d5248997a60117d.zip.