iOS 9.3.6 (build 13G37) is an official Apple over-the-air update for the iPhone 4s, released on 2019-07-22T17:06:58Z. The update package is 22.8 MB. This is a delta (partial) update that requires 9.3.4 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 2d0ecbeca7a020d6af9a9e65bd17a3c9a88e8036.zip.