This indicates an attack attempt to exploit a Remote Code Execution Vulnerability in the WebAdmin of Sophos SG UTM.
The vulnerability is due to insufficient sanitization when handling a malicious request. A remote attacker may be able to exploit this to disclose data or execute arbitrary code within the context of the application, via a crafted HTTP request.
Sophos SG UTM before v9.705 MR5, v9.607 MR7, and v9.511 MR11
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor