While Testing the Company's Web Applications, a Tester Attempts to Insert

While testing the company's web applications, a tester attempts to insert the following test script into the search area on the company's web site: <script>alert(" Testing Testing Testing ") </script> Afterwards, when the tester presses the search button, a pop-up box appears on the screen with the text: "Testing Testing Testing". Which vulnerability has been detected in the web application?

A) Buffer overflow
B) Cross-site request forgery
C) Distributed denial of service
D) Cross-site scripting