This indicates an attack attempt against an Arbitrary File Upload vulnerability in WordPress Front End Editor 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 Front End Editor Plugin 2.2.1 and prior version
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.