iOS 11.2.1 (build 15C153) is an official Apple over-the-air update for the iPhone 8 Plus (GSM), released on 2017-12-13T18:11:03Z. The update package is 399.8 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: 75a5aa0fa7de3bb6a36886e875411fcb1066bb61.zip.