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 iOS before 11.1
Apple Safari before 11.0.1
Apple iCloud before 7.1 on Windows
Apple iTunes before 12.7.1 on Windows
Apple tvOS before 11.1
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply patches or fixes from the vendor, available from the website: