iOS 8.4 (build 12H143) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2015-06-30T15:51:22Z. The update package is 488.3 MB. This is a delta (partial) update that requires 8.1.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: caf0e8c9283e8c17962bd7a41a9e7ec2ad534358.zip.