This issue was addressed with improved checks. This issue is fixed in macOS Big Sur 11.0.1, watchOS 7.0, iOS 14.0 and iPadOS 14.0, iCloud for Windows 7.21, tvOS 14.0. A remote attacker may be able to cause a denial of service.
https://support.apple.com/kb/HT211846
https://support.apple.com/en-us/HT211931
https://support.apple.com/en-us/HT211850
https://support.apple.com/en-us/HT211847
https://support.apple.com/en-us/HT211844