iOS 12.1.3 (build 16D40) is an official Apple over-the-air update for the iPhone XS, released on 2019-01-22T18:15:01Z. The update package is 318.67 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: f571ab62089fdb0f8e39cb9f0c4d3c3fe7fe3d3d.zip.