iOS 11.2.1 (build 15C153) is an official Apple over-the-air update for the iPhone 6s+, released on 2017-12-13T18:13:58Z. The update package is 316.18 MB. This is a delta (partial) update that requires 11.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 3a41d1ca621973d4598da20f913211bfb79807fe.zip.