The attack demonstrated in the scenario is a Cross-site Scripting (XSS) attack. This is evident from the attacker's action of inserting a <script> tag into the URL, which is a common technique used in XSS attacks to execute malicious scripts in the context of the victim's browser. The script in the URL is designed to display an alert box with a warning message, which is a typical behavior of XSS to show that the attacker can execute JavaScript in the user's browser session.
References The answer can be verified through EC-Council's Certified SOC Analyst (CSA) course materials and study guides, which cover various types of cyber attacks, including XSS, and their characteristics.