This indicates an attack attempt to exploit a SQL Injection vulnerability in FreePBX.
The vulnerability is due to insufficient input validation in the application when handling a crafted HTTP request. A remote attacker may be able to execute arbitrary commands in the security context of the target user via a crafted request.
FreePBX Project FreePBX 13.0.47 and prior
System Compromise: Remote attackers can gain control of vulnerable systems.
Currently we are unaware of any vendor supplied patch for this issue.