This indicates an attack attempt to exploit a SQL Injection vulnerability in Advantech WebAccess.
The vulnerability is due to insufficient validation of HTTP parameters when processing HTTP requests. It may allow remote attackers to execute arbitrary SQL statements via a crafted HTTP request which could lead to arbitrary code execution with database privileges.
Advantech WebAccess prior to 8.2_20170817
System Compromise: Remote attackers can add, view, delete or modify data in the database of the affected application
Currently we are unaware of any official fix for this issue.