This indicates an attack attempt against an Arbitrary File Upload vulnerability in WordPress N-Media Website Contact Form plugin.
The vulnerability is due to insufficient sanitizing of user supplied inputs when handling a crafted file upload. It allows a remote attacker to upload an arbitrary file onto vulnerable systems via a crafted HTTP request.
WordPress N-Media Website Contact Form Plugin 1.3.4 and prior
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.