A cross-site scripting issue existed in Safari. This issue was addressed with improved URL validation. This issue affected versions prior to iOS 12.1, watchOS 5.1, Safari 12.0.1, iTunes 12.9.1, iCloud for Windows 7.8.
https://support.apple.com/kb/HT209198
https://support.apple.com/kb/HT209197
https://support.apple.com/kb/HT209196