iOS 12.1.3 (build 16D40) is an official Apple over-the-air update for the iPhone XS Max (China), released on 2019-01-22T18:15:04Z. The update package is 318.35 MB. This is a delta (partial) update that requires 12.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 71b241ea5e042702b2d6057292373adb9076856f.zip.