This indicates an attack attempt to exploit a Directory Traversal Vulnerability in Advantech WebAccess/NMS.
The vulnerability is due to an error in the vulnerable application when handling a maliciously crafted request. An attacker can exploit this to read arbitrary files on the affected machine via a crafted request.
Advantech WebAccess/SCADA 8.3.1 and 8.3.2
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems.
Upgrade to Advantech WebAccess 8.3.3 or later.