Option A. Cross-Site Scripting (XSS) attack is the most probable answer because the scenario centers on session cookies being intercepted and reused by an attacker , leading to overlapping sessions and unauthorized actions. CHFI v11 explicitly includes Investigating Cross-Site Scripting, SQL Injection, and Directory Traversal Attacks and also Investigating Brute Force Attack and Cookie Poisoning Attack under web application forensics.
Among the options provided, XSS is the best fit because it is a common method used to steal or abuse session cookies . Once an attacker obtains a valid session cookie, they can hijack a logged-in session and act as the victim without needing to know the password. That explains unauthorized purchases, profile changes, and simultaneous use of the same session from different locations.
Brute force focuses on guessing passwords, not using intercepted session cookies. SQL injection targets database queries and does not directly explain cookie reuse. Parameter tampering involves modifying request values, but the stronger clue here is stolen session cookies , which aligns more closely with XSS- driven session hijacking. Therefore, under CHFI's web-attack investigation objectives, XSS is the most likely cause among the listed choices.