CVE-2025-40721 is a reflected Cross-site Scripting (XSS) vulnerability identified in the Quiter Gateway product, specifically in versions prior to 4.7.0. Quiter Gateway is a Java WAR application deployed on Apache Tomcat servers. The vulnerability arises from improper neutralization of user-supplied input in the id_factura parameter within the /<Client>FacturaE/listado_facturas_ficha.jsp page. An attacker can craft a malicious URL containing JavaScript code embedded in this parameter, which is then reflected back in the HTTP response without adequate sanitization or encoding. When a victim clicks on such a URL, the malicious script executes in their browser context, potentially allowing the attacker to steal session cookies, perform actions on behalf of the user, or conduct phishing attacks. The vulnerability is classified under CWE-79, indicating improper input handling during web page generation. The CVSS v4.0 base score is 5.1 (medium severity), reflecting that the attack vector is network-based, requires no privileges or authentication, but does require user interaction (clicking the malicious link). The scope is limited to the affected web application component, and the impact is primarily on confidentiality and integrity of the user's session and data. No known exploits are currently reported in the wild, and no official patches are linked yet, though upgrading to version 4.7.0 or later is implied to remediate the issue.

For European organizations using Quiter Gateway, this vulnerability poses a moderate risk. Since Quiter Gateway handles invoice-related data (indicated by the id_factura parameter and FacturaE naming, which aligns with electronic invoicing standards common in Europe), exploitation could lead to unauthorized disclosure of sensitive financial information or session hijacking of users with access to invoicing systems. This could result in financial fraud, data leakage, or disruption of business processes. The reflected XSS attack requires user interaction, typically through phishing or social engineering, which means targeted attacks against employees or partners are plausible. Organizations in sectors such as finance, manufacturing, and public administration that rely on Quiter Gateway for invoice management are particularly at risk. The vulnerability could also undermine trust in digital invoicing workflows and compliance with data protection regulations like GDPR if personal or financial data is exposed.

To mitigate this vulnerability, organizations should promptly upgrade Quiter Gateway to version 4.7.0 or later where the issue is fixed. In the absence of an immediate patch, web application firewalls (WAFs) can be configured to detect and block suspicious input patterns targeting the id_factura parameter. Input validation and output encoding should be enforced on the server side to neutralize any script tags or malicious payloads before reflecting input back to the client. Security teams should conduct phishing awareness training to reduce the risk of users clicking malicious links. Additionally, implementing Content Security Policy (CSP) headers can help restrict the execution of unauthorized scripts in browsers. Regular security assessments and code reviews focusing on input handling in web applications are recommended to prevent similar vulnerabilities.