This indicates an attack attempt to exploit an Elevation Of Privilege Vulnerability in Moodle.
The vulnerability is due to an error in the vulnerable application when handling a maliciously crafted HTTP request. A remote attacker may be able to exploit this to leverage their privileges on vulnerable systems.
Moodle version 3.9
Moodle version 3.8 to 3.8.3
Moodle version 3.7 to 3.7.6
Moodle version 3.5 to 3.5.12
Moodle version prior to above version
Privilege Escalation: Remote attackers can leverage their privileges on vulnerable systems.
Apply the most recent upgrade or patch from the vendor.