watchOS 4.2.3 (build 15S600b) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2018-02-19T21:17:52Z. The update package is 181.84 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: 97e15e6de641348700bd59585f3e678b9d7e309e.zip.