Although a web enabled application appears to only allow letters in the comment field of a web form, malicious user was able to carry a SQL injection attack by sending special characters through the…

A revision control system is used for managing changes to source code and documentation, not for implementing application-level security controls like input validation to prevent SQL injection.

Client-side exception handling deals with errors that occur within the user's browser and does not prevent malicious input from being sent to or processed by the server, as client-side controls can be circumvented.

Server-side validation is critical because client-side validation can be easily bypassed by a malicious user, allowing unvalidated input containing special characters to reach the server. By validating and sanitizing input on the server, the application prevents malicious characters from being interpreted as SQL commands, thereby stopping SQL injection attacks.

Server hardening focuses on securing the operating system, network services, and infrastructure components of a server, but it does not directly address application-level vulnerabilities related to improper input validation within the web application code.