A web application accepts user input for a search query from a form field. What is the best method to ensure the input is safe from injection attacks?
Use a blacklist to reject known harmful characters like single quotes, double quotes, and semicolons.
Require the use of API keys to access the search functionality.
Implement a whitelist to accept only alphanumeric characters in the input.
Encode the output data to the client before displaying it in the web application.