iOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPhone 7 Plus (GSM), released on 2018-04-24T17:11:39Z. The update package is 1.48 GB. This is a delta (partial) update that requires 10.3.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 01b516353f5c9d6060869409f7878bf93614e5d9.zip.