Final answer:
User input validation helps mitigate many cyber threats, such as SQL injection and XSS, but does not prevent phishing attacks, which rely on social engineering tactics.
Step-by-step explanation:
Validating user input on a web application is a critical security measure that helps to mitigate a variety of cyber threats. However, it is important to note that not all types of attacks can be prevented by input validation. For example, phishing attacks, which often involve tricking a user into clicking a malicious link or providing personal information, are not typically stopped by input validation methods. Input validation primarily prevents attacks such as SQL injection, cross-site scripting (XSS), and command injection, which involve malicious data being inserted into an application.