iOS 12.1.3 (build 16D5032a) is an official Apple over-the-air update for the iPhone 6, released on 2018-12-19T18:07:05Z. The update package is 238.86 MB. This is a delta (partial) update that requires 12.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 24e5cf060165b6cf8bc6f53f996352b84d88cf2d.zip.