A custom URL scheme handling issue was addressed with improved input validation. This issue is fixed in Safari 18, iOS 17.7.1 and iPadOS 17.7.1, macOS Sequoia 15, watchOS 11, iOS 18 and iPadOS 18. Maliciously crafted web content may violate iframe sandboxing policy.
https://support.apple.com/en-us/121567
https://support.apple.com/en-us/121250
https://support.apple.com/en-us/121241