A memory corruption issue was addressed with improved validation. This issue is fixed in iOS 12.1.3, macOS Mojave 10.14.3, tvOS 12.1.2, watchOS 5.1.3, iTunes 12.9.3 for Windows. A sandboxed process may be able to circumvent sandbox restrictions.
https://support.apple.com/HT209450
https://support.apple.com/HT209448
https://support.apple.com/HT209447
https://support.apple.com/HT209446