This indicates an attack attempt against an Arbitrary File Upload vulnerability in WordPress Showbiz Pro Responsive Teaser PluginPlugin and Slider Revolution Responsive 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 Slider Revolution Responsive Plugin 3.0.96 and prior
WordPress Showbiz Pro Responsive Teaser Plugin 1.7.1 and prior
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.