iOS 9.3.6 (build 13G37) is an official Apple over-the-air update for the iPhone 4s, released on 2019-07-22T17:06:49Z. The update package is 988.31 MB. This is a delta (partial) update that requires 7.1 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 8a44aa7fc467d49a6566e93ee419a716e287800a.zip.