A logic issue was addressed with improved state management. This issue is fixed in macOS Big Sur 11.0.1, watchOS 7.1, iOS 14.2 and iPadOS 14.2, iCloud for Windows 11.5, tvOS 14.2, iTunes 12.11 for Windows. A local user may be able to read arbitrary files.
http://seclists.org/fulldisclosure/2020/Dec/26
http://seclists.org/fulldisclosure/2020/Dec/32
https://support.apple.com/en-us/HT211928
https://support.apple.com/en-us/HT211929
https://support.apple.com/en-us/HT211930
https://support.apple.com/en-us/HT211931
https://support.apple.com/en-us/HT211933