iOS 9.3.5 (build 13G36) is an official Apple over-the-air update for the iPhone 4s, released on 2016-08-25T16:53:26Z. The update package is 927.96 MB. This is a delta (partial) update that requires 8.1.3 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 6976b07b2df3a3514e18d9de8e2fe9299d627077.zip.