iOS 12.1.3 (build 16D5032a) is an official Apple over-the-air update for the iPhone XS, released on 2018-12-19T18:06:58Z. The update package is 328.05 MB. This is a delta (partial) update that requires 12.1.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 66f366abbab6bbc3b3d51d9cf0191dd1a2357e05.zip.