A memory corruption issue was addressed with improved input validation. This issue affected versions prior to iOS 12, macOS Mojave 10.14, tvOS 12, watchOS 5, iTunes 12.9 for Windows, iCloud for Windows 7.7.
https://support.apple.com/kb/HT209141
https://support.apple.com/kb/HT209140
https://support.apple.com/kb/HT209139
https://support.apple.com/kb/HT209108