This indicates an attack attempt against a Remote Code Execution vulnerability in Pulse Connect Secure.
The vulnerability is due to insufficient sanitizing of user supplied inputs when handling a crafted HTTP request. An authenticated attacker could exploit this to execute arbitrary code in the context of the vulnerable application.
Pulse Connect Secure (PCS) 9.1Rx or below
Pulse Policy Secure (PPS) 9.1Rx or below
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.