watchOS 4.2 (build 15S5090c) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2017-11-06T18:03:42Z. The update package is 180.1 MB. This is a delta (partial) update that requires 4.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6da6941772bc29d3bf1f883dcb63ab61e15c374e.zip.