A memory corruption issue was addressed with improved input validation. This issue is fixed in iOS 13.3.1 and iPadOS 13.3.1, macOS Catalina 10.15.3, tvOS 13.3.1, watchOS 6.1.2. Processing a maliciously crafted string may lead to heap corruption.
https://support.apple.com/HT210921
https://support.apple.com/HT210920