This indicates an attack attempt to exploit an Use After Free Vulnerability in Foxit Reader.
The vulnerability is due to an error in the vulnerable application when handling a maliciously crafted PDF file. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted PDF file.
Foxit Reader 188.8.131.529 and prior
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor: