CVE-2025-51503 is a Stored Cross-Site Scripting (XSS) vulnerability identified in Microweber CMS version 2.0. This vulnerability allows attackers to inject malicious JavaScript code into user profile fields within the CMS. Because these fields are stored and later rendered in the administrative interface without proper sanitization or encoding, the injected scripts execute in the context of the admin's browser session. This can lead to arbitrary JavaScript execution, enabling attackers to perform actions such as session hijacking, privilege escalation, or unauthorized administrative operations. Stored XSS is particularly dangerous because the malicious payload persists on the server and affects any admin user who views the compromised profile data. The vulnerability does not have an assigned CVSS score, and no public exploits have been reported yet. However, given the nature of stored XSS and its impact on administrative users, this vulnerability poses a significant risk to the confidentiality and integrity of the CMS environment.

For European organizations using Microweber CMS 2.0, this vulnerability could result in severe security breaches. Attackers exploiting this flaw can gain unauthorized access to administrative functions, potentially leading to website defacement, data theft, or further compromise of backend systems. The ability to execute arbitrary JavaScript in admin browsers can also facilitate the deployment of additional malware or pivoting attacks within the organization's network. Given that many European businesses rely on CMS platforms for their web presence, exploitation could damage brand reputation, lead to regulatory non-compliance (e.g., GDPR violations due to data exposure), and cause operational disruptions. The impact is heightened in sectors with sensitive data or critical infrastructure, where administrative account compromise can have cascading effects.

To mitigate this vulnerability, organizations should immediately review and sanitize all user input fields, especially those related to user profiles, to ensure that scripts or HTML tags are properly escaped or removed before storage and rendering. Applying strict Content Security Policies (CSP) can help limit the execution of unauthorized scripts in admin browsers. Since no patch links are currently available, organizations should consider temporarily restricting or closely monitoring administrative access to the CMS and auditing user profile data for suspicious content. Additionally, implementing multi-factor authentication (MFA) for admin accounts can reduce the risk of session hijacking. Regular security assessments and penetration testing focused on input validation and XSS vulnerabilities are recommended. Once an official patch or update is released by Microweber, it should be applied promptly.