iOS 12.1.3 (build 16D39) is an official Apple over-the-air update for the iPhone 8 (GSM), released on 2019-01-22T18:09:01Z. The update package is 1.45 GB. This is a delta (partial) update that requires 11.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 81dce0c5f4e7562339ff0966c7bd19451d203f2d.zip.