iOS 9.9.11.2.1 (build 15C153) is an official Apple over-the-air update for the iPhone 6s, released on 2017-12-13T18:13:28Z. The update package is 1.29 GB. This is a delta (partial) update that requires 9.3.4 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6d3c1754410f43d92ef05abc9d45adfa7699f84e.zip.