CVE-2025-26877 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 Rustaurius Front End Users product, specifically versions up to 3.2.30. The flaw allows an attacker to inject malicious scripts that are stored persistently (Stored XSS) and later executed in the browsers of users who access the compromised content. The vulnerability arises from insufficient input sanitization or output encoding during web page generation, enabling attackers to embed arbitrary JavaScript code. When executed, this code can hijack user sessions, steal cookies, perform actions on behalf of the user, or redirect users to malicious sites. The CVSS v3.1 base score is 6.5, indicating a medium severity level. The vector string (AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L) shows that the attack is network exploitable with low attack complexity, requires low privileges, and user interaction is necessary. The scope is changed, meaning the vulnerability affects components beyond the initially vulnerable component, and the impact includes low confidentiality, integrity, and availability losses. No known exploits are currently reported in the wild, and no patches have been linked yet. This vulnerability is significant because stored XSS can have persistent effects and impact multiple users, especially in web applications with many front-end users.

For European organizations using Rustaurius Front End Users, this vulnerability poses risks to data confidentiality, user trust, and operational integrity. Exploitation could lead to session hijacking, unauthorized actions, and potential data leakage, which may violate GDPR requirements on data protection and user privacy. Organizations in sectors such as finance, healthcare, and government, where sensitive user data is handled, are particularly vulnerable. The persistent nature of stored XSS means that malicious scripts can affect multiple users over time, increasing the attack surface. Additionally, reputational damage and regulatory penalties could result from successful exploitation. The requirement for user interaction (e.g., clicking a link or viewing a page) means social engineering could be used to trigger attacks. The medium severity score suggests that while the vulnerability is not critical, it still requires timely remediation to prevent exploitation.

European organizations should implement the following specific mitigations: 1) Apply strict input validation and output encoding on all user-supplied data within the Rustaurius Front End Users application, focusing on HTML, JavaScript, and URL contexts. 2) Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of XSS attacks. 3) Monitor and sanitize stored content regularly to detect and remove any malicious scripts that may have been injected prior to patching. 4) Educate users about the risks of clicking unknown links or interacting with suspicious content to reduce the likelihood of triggering stored XSS. 5) Coordinate with Rustaurius vendor support to obtain and apply patches or updates as soon as they become available. 6) Conduct security testing, including automated scanning and manual code reviews, to identify and remediate similar input validation issues. 7) Implement multi-factor authentication to limit the impact of session hijacking resulting from XSS exploitation.