A use after free issue was addressed with improved memory 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, Safari 14.0.1, tvOS 14.2, iTunes 12.11 for Windows. Processing maliciously crafted web content may lead to arbitrary code execution.
https://www.debian.org/security/2021/dsa-4877
https://support.apple.com/en-us/HT211935
https://support.apple.com/en-us/HT211934
https://support.apple.com/en-us/HT211933
https://support.apple.com/en-us/HT211931
https://support.apple.com/en-us/HT211930
https://support.apple.com/en-us/HT211929
https://support.apple.com/en-us/HT211928
https://security.gentoo.org/glsa/202104-03