This indicates an attack attempt to exploit an Unrestricted File Upload vulnerability in PrestaShop.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application. A remote, unauthenticated attacker can exploit this vulnerability by uploading a malicious file to the targeted server. Successful exploitation would lead to execution of arbitrary code in the security context of SYSTEM or root on the server.
PrestaShop 1.6 and 1.7
System Compromise: Remote attackers can gain control of vulnerable systems.
Currently we are unaware of any vendor supplied patch for this issue.