iOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPhone 7 Plus (GSM), released on 2018-04-24T17:11:38Z. The update package is 1.53 GB. This is a delta (partial) update that requires 10.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 4c9bca4a0668dc2c25c2325049a25d3258f05aad.zip.