MacRumors published a story that Apple has released macOS Big Sur 11.6.1 beta to registered developers.

Apple Seeds macOS Big Sur 11.6.1 Beta to Developers With Security Fixes

Apple today seeded a macOS Big Sur 11.6.1 beta to developers for testing purposes, with the update coming two weeks after the launch of macOS Big Sur 11.6. Registered developers can download the beta through the Apple Developer Center and once the appropriate profile is installed, betas will be available through the Software Update mechanism in System Preferences. According to Apple's release notes, the update "improves the security of macOS." It's not clear why it's being released as a beta rather than to all users, but there's also a developer beta of a security update available for macOS Catalina as well.

Apple Seeds macOS Big Sur 11.6.1 Beta to Developers With Security Fixes