iOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPhone X (Global), released on 2018-04-24T17:09:29Z. The update package is 781.55 MB. This is a delta (partial) update that requires 11.1.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 29e2a4669a693f087a3f7a2e8752154d6471f351.zip.