This indicates an attack attempt to exploit a SQL Injection vulnerability in Icegram Email Subscribers & Newsletters plugin through 4.1.7 for WordPress.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application. A remote attacker can exploit this to send a crafted request to execute SQL commands on a vulnerable target.
Icegram Email Subscribers & Newsletters plugin through 4.1.7
System Compromise: Remote attackers can access or modify data in the database of the affected application
Apply the most recent upgrade or patch from the vendor.