iOS 12.1.3 (build 16D39) is an official Apple over-the-air update for the iPhone 6, released on 2019-01-22T18:10:28Z. The update package is 1.33 GB. This is a delta (partial) update that requires 11.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: a258192b05479a034d11d257ca933efa58fa6478.zip.