During a penetration testing engagement, your team has identified an application that is vulnerable to command injection due to insufficient input validation. In your final report, what is the most appropriate process-level remediation recommendation to address this specific vulnerability?
Advise the client to update their application frameworks to the latest versions to avoid command injection.
Recommend the implementation of proper input sanitization and the use of prepared statements or parameterized queries.
Suggest increasing the complexity of input validation rules within the application code.
Instruct the client to configure the existing Web Application Firewall (WAF) to block command injection attacks.