This indicates an attack attempt to perform an Arbitrary File Upload vulnerability in Joomla Facileforms Plugin.
The vulnerability is due to a design flaw in the vulnerable application when handling a file upload request without authentication. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, by uploading an arbitrary file without any authentication.
Joomla Facileforms Plugin
System Compromise: Remote attackers can gain control of vulnerable systems.
Currently, we are unaware of any vendor supplied patch for this issue.