Apple has released watchOS 7.6.1 (build 18U70) for download for Apple Watch users.
You can download and install watchOS 7.6.1 by launching the Watch app on your iPhone, then going to General > Software Update. You will need to have iOS 14.7.1 installed first, which was released on Monday.
The update is still propagating in Canada as of writing and likely will contain security fixes as with the iOS and iPadOS 14.7.1 updates.
Update July 28, 2021: Looks like this update has been pulled by Apple, as it’s no longer listed on its developer website.
Update July 29, 2021: The update has been released just now and Apple says it contains “important security updates”. The download size is 64.2MB: