iOS 8.4 (build 12H4125a) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2015-06-09T17:53:06Z. The update package is 161.97 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: 1fbff939508aeec58c397f939f2996d5f3ba4657.zip.