iOS 12.1 (build 16B5077c) is an official Apple over-the-air update for the iPhone XS Max, released on 2018-10-09T17:05:45Z. The update package is 322.18 MB. This is a delta (partial) update that requires 12.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 8c5396a93167fc72c3e1c12a230a9e1c88be6eeb.zip.