Multiple memory corruption issues were addressed with improved memory handling. This issue is fixed in iOS 12.3, macOS Mojave 10.14.5, tvOS 12.3, Safari 12.1.1, iTunes for Windows 12.9.5, iCloud for Windows 7.12. Processing maliciously crafted web content may lead to arbitrary code execution.
https://support.apple.com/HT210118
https://support.apple.com/HT210119
https://support.apple.com/HT210120
https://support.apple.com/HT210123
https://support.apple.com/HT210124