Apple has released watchOS 8.4.1, which provides bug fixes and security updates for the Apple Watch Series 4 and later.
watchOS 8.4.1 can be downloaded for free through the dedicated Apple Watch app on the iPhone by going to General > Software Update. To install the new software, the Apple Watch needs to have at least 50% battery, it needs to be placed on a charger, and it needs to be in range of the iPhone.