CVE-2025-41053 is a stored Cross-Site Scripting (XSS) vulnerability identified in appRain CMF version 4.0.5. This vulnerability arises from improper neutralization of user input during web page generation, specifically within the parameters 'data[Addon][layouts]' and 'data[Addon][layouts_except]' in the endpoint /apprain/developer/addons/update/commonresource. Because these parameters are not properly validated or sanitized, an authenticated attacker can inject malicious scripts that are stored on the server and subsequently executed in the browsers of users who access the affected pages. The vulnerability is classified under CWE-79, which pertains to improper input validation leading to XSS. The CVSS v4.0 base score is 5.1, indicating a medium severity level. The vector string (CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N) shows that the attack can be performed remotely over the network without requiring special privileges beyond authentication, with low attack complexity and no need for user interaction other than the victim viewing the malicious content. The scope is limited (SI:L), and there is no impact on confidentiality, integrity, or availability (VC:N/VI:N/VA:N). No known exploits are currently reported in the wild, and no official patches have been linked yet. The vulnerability allows attackers to execute arbitrary JavaScript in the context of the affected web application, potentially leading to session hijacking, defacement, or redirection to malicious sites. However, the requirement for authentication limits the attack surface to users with some level of access to the system.

For European organizations using appRain CMF 4.0.5, this vulnerability poses a moderate risk. Since the exploit requires authentication, the threat is primarily from insider threats or compromised user accounts. Successful exploitation could allow attackers to execute malicious scripts within the context of the web application, potentially leading to session theft, unauthorized actions, or phishing attacks against other users. This could undermine user trust, lead to data leakage, or facilitate further attacks within the network. Given the medium CVSS score and the lack of direct impact on confidentiality, integrity, or availability, the immediate damage may be limited. However, if leveraged as part of a broader attack chain, it could contribute to significant security incidents. European organizations with sensitive data or regulatory obligations (e.g., GDPR compliance) should be particularly cautious, as exploitation could result in data breaches or non-compliance penalties. The lack of known exploits in the wild reduces immediate urgency but does not eliminate the risk of future exploitation.

Organizations should implement strict input validation and output encoding on the affected parameters ('data[Addon][layouts]' and 'data[Addon][layouts_except]'). Until an official patch is released, applying web application firewalls (WAFs) with custom rules to detect and block suspicious payloads targeting these parameters can reduce risk. Limiting user privileges to the minimum necessary and monitoring authenticated user activities for anomalous behavior can help detect potential exploitation attempts. Regularly auditing and reviewing addon updates and developer endpoints for unusual input patterns is advisable. Additionally, organizations should ensure that session management is robust (e.g., HttpOnly and Secure cookies) to mitigate session hijacking risks. Promptly applying patches once available and maintaining an up-to-date inventory of appRain CMF deployments will facilitate rapid response. Security awareness training for users with access to the system can reduce the risk of social engineering that might lead to account compromise.