iOS 12.1.2 (build 16C101) is an official Apple over-the-air update for the iPhone XS, released on 2018-12-17T21:06:18Z. The update package is 493.71 MB. This is a delta (partial) update that requires 12.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 9743f778c6fabe4a087d5f362e74f39469f5f2d2.zip.