Which of the following is the BEST method to discover the vulnerability before a production deployment?

A web application has a newly discovered vulnerability in the authentication method used to validate known company users. The user ID of Admin with a password of “password” grants elevated access to the application over the Internet .

Which of the following is the BEST method to discover the vulnerability before a production deployment?
A . Manual peer review
B . User acceptance testing
C . Input validation
D . Stress test the application

Answer: C