iOS 12.1.3 (build 16D5032a) is an official Apple over-the-air update for the iPhone 6s, released on 2018-12-19T18:07:05Z. The update package is 224.76 MB. This is a delta (partial) update that requires 12.1.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 67ead20805dd3a66ebef9e4117a24e7483788174.zip.