iOS 12.1.3 (build 16D40) is an official Apple over-the-air update for the iPhone XS Max (China), released on 2019-01-22T18:15:05Z. The update package is 317.98 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: 50d6b0377cd0314a357e7be29072898307ea9623.zip.