This indicates an attack attempt to exploit a Command Injection Vulnerability in Nagios Enterprises Nagios XI.
This vulnerability is due to insufficient validation of the input parameters in the mibs.php. A remote, authenticated attacker could exploit this vulnerability by sending crafted requests to the target system. Successful exploitation results in the execution of arbitrary commands with the web server privilege on the target server.
Nagios Enterprises Nagios XI prior to 5.7.4
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.