This indicates an attempt to exploit a Use After Free vulnerability in Apple WebKit.
The vulnerability is due to an error when the vulnerable software attempts to handles maliciously crafted web page. An attacker can exploit this to execute arbitrary code via a crafted web page.
Apple before iOS 12
Apple before tvOS 12
Apple before Safari 12
Apple before iTunes 12.9 for Windows
Apple before iCloud for Windows 7.7
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply patches or fixes from the vendor, available from the website: