This indicates an attack attempt to exploit an Code Execution Vulnerability in D-Link Central WiFiManager.
The vulnerability is due to hard-coded credentials in the FTP server. A remote attacker can exploit this to upload and execute arbitrary php code on affected devices.
D-Link Central WiFi Manager before v 1.03r0100-Beta1
System Compromise: Remote attackers can gain control of vulnerable systems.
Refer to the vendor's advisory for updates: