iOS 12.1.3 (build 16D39) is an official Apple over-the-air update for the iPhone X (GSM), released on 2019-01-22T18:09:21Z. The update package is 1.54 GB. This is a delta (partial) update that requires 11.4 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 65c06711d5ee8d2a81522ec2eb531d7fb65940b5.zip.