This issue was addressed through improved state management. This issue is fixed in Safari 26.5.2, iOS 26.5.2 and iPadOS 26.5.2, macOS Tahoe 26.5.2, tvOS 26.6, visionOS 26.6, watchOS 26.6. A malicious website may be able to silently hijack clipboard data.
https://isc.sans.edu/diary/rss/33114
https://support.apple.com/en-us/128070
https://support.apple.com/en-us/128069
https://support.apple.com/en-us/128068
https://support.apple.com/en-us/127685