SQL Injection vulnerability exists in Sourcecodester Simple Client Management System 1.0 via the id parameter in view-service.php.
https://r4hn1.medium.com/journey-to-first-two-cve-by-rahul-kalnarayan-307e2e87ee26
https://github.com/r4hn1/Simple-Client-Management-System-Exploit/blob/main/CVE-2021-43509