Multiple memory corruption issues were addressed with improved memory handling. This issue affected versions prior to iOS 12.1.1, tvOS 12.1.1, watchOS 5.1.2, Safari 12.0.2, iTunes 12.9.2 for Windows, iCloud for Windows 7.9.
https://support.apple.com/kb/HT209346
https://support.apple.com/kb/HT209345
https://support.apple.com/kb/HT209344
https://support.apple.com/kb/HT209343