A vulnerability exists in ChurchCRM 5.13.0 and prior that allows an attacker to execute arbitrary SQL queries by exploiting a boolean-based blind SQL Injection vulnerability in the EditEventAttendees functionality. The EID parameter is directly concatenated into an SQL query without proper sanitization, making it susceptible to SQL injection attacks. An attacker can manipulate the query, potentially leading to data exfiltration, modification, or deletion.  Please note that this vulnerability requires Administrator privileges.