A use after free issue was addressed with improved memory management. This issue is fixed in iOS 12.2, tvOS 12.2, Safari 12.1, iTunes 12.9.4 for Windows, iCloud for Windows 7.11. Processing maliciously crafted web content may lead to arbitrary code execution.
https://support.apple.com/HT209605
https://support.apple.com/HT209604
https://support.apple.com/HT209603