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 before 9.1R11.4
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.