PrestaShop is an open source e-commerce web application. Prior to 8.2.6 and 9.1.1, there is a stored Cross-Site Scripting (XSS) vulnerability in the PrestaShop back-office Customer Service view. An unauthenticated attacker can submit the public Contact Us form with a malicious email address. The payload is stored in the database and executed when a back-office employee opens the affected customer thread, enabling session hijacking and full back-office takeover. This vulnerability is fixed in 8.2.6 and 9.1.1.