CVE-2025-41048 is a stored Cross-Site Scripting (XSS) vulnerability identified in version 4.0.5 of the appRain CMF (Content Management Framework). This vulnerability arises from improper neutralization of user input during web page generation, specifically within the 'data[Addon][layouts]' and 'data[Addon][layouts_except]' parameters accessed via the /apprain/developer/addons/update/admin endpoint. Because the input is not properly validated or sanitized, an authenticated user can inject malicious scripts that are stored on the server and subsequently executed in the browsers of other users who access the affected pages. The vulnerability requires low privileges (authenticated user) and some user interaction (visiting the affected page), but does not require any additional authentication bypass or elevated privileges. The CVSS 4.0 base score is 5.1, reflecting a medium severity level. The attack vector is network-based, with low attack complexity, no privileges required beyond authentication, and user interaction needed. The vulnerability does not impact confidentiality, integrity, or availability directly but can be leveraged to execute arbitrary JavaScript in victims’ browsers, potentially leading to session hijacking, defacement, or further exploitation. No known exploits are currently reported in the wild, and no patches have been published yet. The vulnerability was reserved in April 2025 and published in September 2025 by INCIBE.

For European organizations using appRain CMF 4.0.5, this vulnerability poses a moderate risk. Since the vulnerability allows stored XSS, attackers can inject malicious scripts that execute in the context of authenticated users’ browsers, potentially leading to theft of session cookies, unauthorized actions on behalf of users, or distribution of malware. This can compromise user trust, lead to data leakage, and damage organizational reputation. The impact is particularly significant for organizations that rely on appRain CMF for managing sensitive or customer-facing web content, such as government portals, educational institutions, or e-commerce platforms. Given the authenticated nature of the exploit, insider threats or compromised user accounts could be leveraged to exploit this vulnerability. The lack of a patch increases the window of exposure. However, the absence of known active exploitation reduces immediate risk. European organizations should be vigilant, especially those with high user interaction on the affected modules.

1. Immediate mitigation should include restricting access to the /apprain/developer/addons/update/admin endpoint to trusted administrators only, using network-level controls or web application firewalls (WAFs) with rules to detect and block suspicious input patterns in the affected parameters. 2. Implement strict input validation and output encoding on the server side for the 'data[Addon][layouts]' and 'data[Addon][layouts_except]' parameters to neutralize any injected scripts. 3. Monitor logs for unusual activity or unexpected input submissions to detect potential exploitation attempts. 4. Enforce strong authentication and session management to reduce the risk of compromised accounts being used to exploit this vulnerability. 5. Educate administrators and users about the risks of XSS and encourage cautious behavior when interacting with the CMS. 6. Once available, promptly apply official patches or updates from the vendor. 7. Consider deploying Content Security Policy (CSP) headers to limit the impact of any injected scripts. 8. Conduct regular security assessments and penetration testing focusing on authenticated areas of the CMS.