A security analyst discovered that the company's WAF was not properly configured. The main web server was breached, and the following payload was found in one o...

A security analyst discovered that the company's WAF was not properly configured. The main web server was breached, and the following payload was found in one of the malicious requests:
Which of the following would BEST mitigate this vulnerability?

A. CAPTCHA B. Input validation C. Data encoding D. Network intrusion prevention