CVE-2025-47828 is a medium severity vulnerability classified under CWE-79, which pertains to improper neutralization of input during web page generation, commonly known as Cross-site Scripting (XSS). This vulnerability affects the Lumi H5P-Nodejs-library versions prior to 9.3.3. The root cause is the omission of a sanitizeHtml call for plain text strings, which means that user-supplied input is not properly sanitized before being rendered in a web page context. This allows an attacker to inject malicious scripts into web pages generated by the library. When these scripts execute in the context of a victim's browser, they can lead to unauthorized actions such as session hijacking, defacement, or redirection to malicious sites. The CVSS v3.1 score is 6.4, reflecting a medium severity level with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), requiring low privileges (PR:L), no user interaction (UI:N), scope change (S:C), and partial impact on confidentiality and integrity (C:L/I:L) but no impact on availability (A:N). The scope change (S:C) indicates that the vulnerability affects resources beyond the security scope of the vulnerable component, potentially impacting other components or users. No known exploits are currently reported in the wild, but the vulnerability's presence in a widely used Node.js library for H5P content means that exploitation could be feasible in environments where this library is integrated. The Lumi H5P-Nodejs-library is used to create and manage interactive HTML5 content, often embedded in educational platforms and content management systems, which increases the risk of exposure to end users if the vulnerability is exploited.

For European organizations, the impact of this XSS vulnerability can be significant, especially for those using Lumi's H5P-Nodejs-library in educational technology platforms, e-learning portals, or content management systems. Exploitation could lead to unauthorized access to user sessions, theft of sensitive information such as authentication tokens or personal data, and manipulation of displayed content. This could undermine user trust, lead to data protection violations under GDPR, and cause reputational damage. Since the vulnerability allows scope change, it may enable attackers to affect other components or users beyond the immediate application, potentially escalating the impact. The lack of required user interaction means attacks can be automated and executed remotely, increasing the risk of widespread exploitation if the vulnerability is not addressed. Although no exploits are known in the wild yet, the medium severity and ease of exploitation (low complexity, network vector) suggest that attackers could develop exploits rapidly once the vulnerability is public knowledge. Organizations in sectors with high reliance on interactive web content, such as education, government digital services, and media, are particularly at risk.

European organizations should prioritize upgrading the Lumi H5P-Nodejs-library to version 9.3.3 or later, where the sanitizeHtml call for plain text strings is properly implemented. Until the upgrade is applied, organizations should implement additional input validation and output encoding at the application level to mitigate XSS risks. Employing Content Security Policy (CSP) headers can help restrict the execution of unauthorized scripts. Regular security audits and code reviews of any custom integrations with the H5P library should be conducted to detect and remediate unsafe input handling. Monitoring web application logs for unusual script injection attempts and employing Web Application Firewalls (WAFs) with rules targeting XSS patterns can provide additional protection. Since the vulnerability does not require user interaction, automated scanning tools should be used to detect vulnerable instances across the network. Finally, educating developers and content creators about secure coding and content sanitization best practices will reduce the risk of similar vulnerabilities.