This indicates an attack attempt to exploit an Arbitrary File Upload vulnerability in Trend Micro Mobile Security Enterprise.
The vulnerability is caused by an error when the application handles a malicious upload_img_file request. A remote attacker can exploit this to send a crafted HTTP POST request to execute arbitrary code on vulnerable systems.
Trend Micro Mobile Security (Enterprise) prior to 9.7 Patch 3 (b2406)
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrades or patches from the vendor.