iOS 12.1.3 (build 16D5039a) is an official Apple over-the-air update for the iPhone 6s+, released on 2019-01-10T18:09:12Z. The update package is 229.84 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: 7120eb7ddd8fcc3e4fb2740bc1553b05d643f1bd.zip.