iOS 12.1.3 (build 16D5032a) is an official Apple over-the-air update for the iPhone 6s+, released on 2018-12-19T18:07:06Z. The update package is 240.62 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: 120dc95cc6f304a08470a9f6828f8e3696254bec.zip.