iOS 8.4.1 (build 12H321) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2015-08-13T18:05:14Z. The update package is 55.94 MB. This is a delta (partial) update that requires 8.4 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 7e0154b1f0d829d42b78150f20d68634ed8570df.zip.