CVE-2025-5591 identifies a stored cross-site scripting (XSS) vulnerability in Kentico Xperience version 13.0.167, a widely used web content management system. The root cause is improper neutralization of user input during web page generation within a form component, allowing malicious scripts to be stored and later executed in the browsers of users who access the affected pages. This vulnerability falls under CWE-79 (Improper Neutralization of Input During Web Page Generation) and CWE-1188 (Improper Access of Indexable Resource in a Collection). An attacker can exploit this flaw by injecting malicious JavaScript payloads into form fields that are stored and rendered without adequate sanitization. When a victim user visits the compromised page, the script executes in their security context, enabling session hijacking, credential theft, or unauthorized actions on behalf of the user. The CVSS 4.0 score of 7.7 indicates a high-severity issue with network attack vector, low attack complexity, no privileges required, but requiring user interaction. The vulnerability affects Kentico Xperience 13.0.167, and no patches or known exploits are currently reported. Given the nature of stored XSS, the impact can be severe, especially in environments where users have elevated privileges or access sensitive data. The vulnerability's presence in a popular CMS platform increases the attack surface, as many organizations rely on Kentico for their web presence and digital services.

For European organizations, this vulnerability poses significant risks including session hijacking, unauthorized actions performed under the victim's credentials, and potential data breaches. Public-facing websites using Kentico Xperience 13.0.167 are particularly vulnerable, potentially exposing customers, employees, or partners to malicious scripts. This can lead to reputational damage, regulatory penalties under GDPR due to compromised personal data, and operational disruptions if attackers manipulate web content or user sessions. Organizations in sectors such as finance, healthcare, government, and e-commerce, which often use CMS platforms for customer interaction, are at heightened risk. The stored nature of the XSS means that once injected, the malicious payload can affect multiple users over time, amplifying the impact. Additionally, the vulnerability could be leveraged as a foothold for further attacks within the network if attackers gain access to privileged user sessions.

1. Apply vendor patches immediately once they become available for Kentico Xperience 13.0.167 to remediate the vulnerability at the source. 2. Until patches are released, implement strict input validation and output encoding on all form components to neutralize potentially malicious scripts. 3. Deploy and enforce Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers. 4. Conduct regular security audits and code reviews focusing on input handling and sanitization mechanisms within the CMS. 5. Monitor web application logs and user sessions for unusual activities indicative of XSS exploitation attempts, such as unexpected script execution or session anomalies. 6. Educate users about the risks of interacting with suspicious links or forms, reducing the likelihood of successful exploitation. 7. Consider implementing Web Application Firewalls (WAFs) with rules designed to detect and block XSS payloads targeting Kentico components. 8. Limit user privileges on the CMS to the minimum necessary to reduce the impact of compromised sessions.