This indicates an attack attempt to exploit a Command Execution vulnerability in Trend Micro InterScan Web Security Virtual Appliance (IWSVA).
The vulnerability is due to improper validation of HTTP request parameters in the application. A remote attacker may be able to exploit this to execute arbitrary command within the context of the process, via a crafted HTTP request.
Trend Micro InterScan Web Security Virtual Appliance 6.5 prior to 6.5 CP 1746
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.