iOS 9.3.5 (build 13G36) is an official Apple over-the-air update for the iPhone 4s, released on 2016-08-25T16:53:27Z. The update package is 227.45 MB. This is a delta (partial) update that requires 9.1 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: f95d88df7d2d2cb63f40514d2ef138c2edcd27a3.zip.