iOS 9.3.6 (build 13G37) is an official Apple over-the-air update for the iPhone 4s, released on 2019-07-22T17:06:57Z. The update package is 52.18 MB. This is a delta (partial) update that requires 9.3.1 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 64e567fb4485af111498e6657865a51712744be7.zip.