This indicates an attack attempt against a Command Injection vulnerability in ImageMagick.
The vulnerability is caused by insufficient sanitizing of the filename that is passed to delegate's command. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted file.
ImageMagick before 7.0.1-1 and 6.9.3-10
System Compromise: Remote attacker can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.