watchOS 4.2.3 (build 15S600b) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2018-02-19T21:17:53Z. The update package is 179.55 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: 988611d78dd0a2ef7fc05b491538e95b78c8266b.zip.