iOS 12.1.3 (build 16D5032a) is an official Apple over-the-air update for the iPhone X (GSM), released on 2018-12-19T18:06:56Z. The update package is 295.87 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: 5e06e213a9a8ac23263fc8b6c87cd5ff1739dc19.zip.