This indicates an attack attempt to exploit an Open Redirect vulnerability in Symantec Endpoint Protection Manager (SEPM).
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application. An attacker can exploit this by tricking an unsuspecting user into opening an crafted URL, leading to further attacks.
Symantec Endpoint Protection Manager and client 12.1
System Compromise: Remote attackers can gain control of vulnerable systems.
Refer to the vendor's advisory for updates: