This indicates an attack attempt to exploit a Cross Site Scripting vulnerability in Advantech WebAccess software.
The vulnerability is due to input validation error that occurs in the application when handling maliciously crafted HTTP request. A remote attacker may be able to exploit this to execute arbitrary script code within the context of the application, via a crafted HTTP request.
Advantech WebAccess/SCADA 8.3.1 and 8.3.2
System Compromise: Remote attackers can execute arbitrary script code in the context of the affected server.
Upgrade to Advantech WebAccess 8.3.3 or later.