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>

Buffer overflow involves writing data beyond allocated memory boundaries in an application, not injecting scripts that execute in a browser.

Cross-site request forgery (CSRF) tricks authenticated users into submitting unintended requests to a site where they are logged in, and does not involve injecting executable scripts into input fields.

Distributed denial of service floods a target with traffic from multiple sources to exhaust resources, which has no relation to script injection in a search field.

Cross-site scripting occurs when an application accepts unsanitized user input and reflects or stores it so browsers execute it as script. The pop-up appearing confirms the <script> tag was rendered and executed by the browser rather than treated as plain text, which is the defining characteristic of a reflected XSS vulnerability.