A type confusion issue was addressed with improved memory handling. This issue is fixed in Safari 15.1, tvOS 15.1, iOS 15 and iPadOS 15, macOS Monterey 12.0.1, watchOS 8.1. Processing maliciously crafted web content may lead to code execution.
https://support.apple.com/en-us/HT212876
https://support.apple.com/en-us/HT212875
https://support.apple.com/en-us/HT212874