Apple released watchOS 4.0.1 on Wednesday with a fix for a problem where some Apple Watch Series 3 models with cellular connectivity support were connecting to unauthenticated public Wi-Fi networks.
The update addresses what could be a security issue because not all public Wi-Fi networks can be trusted. Someone networks could, for example, be traps trying to siphon personal information from your watch or computer.
To install watchOS 4.0.1, launch the Watch app on your iPhone, then go to My Watch > General > Software Update. If the update is available for your Apple Watch it’ll appear there.