This indicates an attack attempt to exploit a Security Bypass vulnerability in the InduSoft Web Studio and InTouch Edge HMI.
The vulnerability is due to improper authentication in the vulnerable application when handling a malicious request. A remote attacker may be able exploit this to execute arbitrary code on vulnerable machines.
InduSoft Web Studio versions prior to 8.1 SP2
InTouch Edge HMI (formerly InTouch Machine Edition) versions prior to 2017 SP2
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.