This indicates an attack attempt against a Buffer Overflow Vulnerability in WebkitGTK+.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application.
WebKitGTK+ version 2.20.3 and prior
WPE WebKit version 2.20.1 and prior
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.