iOS 13.3.1 (build 17D5050a) is an official Apple over-the-air update for the iPhone 6s+, released on 2020-01-22T18:07:29Z. The update package is 102.9 MB. This is a delta (partial) update that requires 13.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6f8d2ec885765464ed15c7d0d3e87fc529f88457.zip.