iOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPhone 7 Plus (GSM), released on 2018-04-24T17:11:42Z. The update package is 744.4 MB. This is a delta (partial) update that requires 11.2.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: ac45b2d785bef29e367dd6bb225b76318c4450da.zip.