This indicates an attack attempt against a Directory Traversal vulnerability in FreePBX Framework.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application while handling maliciously crafted requests to /admin/ajax.php. A remote attacker can exploit this to download arbitrary file from the target server via a crafted request.
FreePBX Project hotelwakeup Module prior to 13.0.15
FreePBX Project FreePBX Framework 13.x
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the latest update from the vendor.