iOS 11.2.1 (build 15C153) is an official Apple over-the-air update for the iPhone X (Global), released on 2017-12-13T18:11:00Z. The update package is 410.55 MB. This is a delta (partial) update that requires 11.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 08328fa51146dba6f876bfc59bb821324a3f9eae.zip.