iOS 12.1.3 (build 16D5037a) is an official Apple over-the-air update for the iPhone XS Max, released on 2019-01-07T18:07:13Z. The update package is 136.34 MB. This is a delta (partial) update that requires 12.1.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 72547e93bd2d4be2ddbd4f713dffe1c03bf5d1d3.zip.