This indicates an attack attempt to exploit a Remote Command Injection vulnerability in elFinder before 2.1.48.
The vulnerability is due to an error when the vulnerable software handles a maliciously crafted HTTP request. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application.
elFinder 2.1.47 or prior
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.