This indicates an attack attempt to exploit a Type Confusion vulnerability in Apple WebKit.
The vulnerability is due to an error when the vulnerable software handles a maliciously crafted web page. An attacker can exploit this by tricking an unsuspecting user into visiting a malicious webpage and execute arbitrary code within the context of the application.
WebKit in iOS prior to 12.1
WebKit in tvOS prior to 12.1
WebKit in watchOS prior to 5.1
WebKit in Safari prior to 12.0.1
WebKit in iTunes prior to 12.9.1
WebKit in iCloud for Windows 7.8
System Compromise: Remote attackers can execute arbitrary script code within the context of the target user's browser.
Apply the most recent upgrade or patch from the vendor.