CVE-2025-51662 is a stored cross-site scripting (XSS) vulnerability identified in FileCodeBox version 2.2 and earlier. The vulnerability stems from insufficient input validation in the text sharing feature, which allows attackers to inject arbitrary JavaScript payloads into shared 'codeboxes'. When a user accesses a compromised codebox by clicking a shared link or entering a share code, the malicious script executes automatically within their browser context. This execution can lead to unauthorized actions such as session hijacking, credential theft, or manipulation of displayed content, impacting confidentiality and integrity. The vulnerability requires low attacker privileges (PR:L) and user interaction (UI:R) but no physical or local access, as it is exploitable remotely over the network (AV:N). The CVSS v3.1 base score is 5.4, indicating medium severity, with a scope change (S:C) meaning the vulnerability affects resources beyond the initially vulnerable component. No public exploits have been reported to date, but the risk remains significant for users of vulnerable versions. The vulnerability is categorized under CWE-79 (Improper Neutralization of Input During Web Page Generation), a common and well-understood class of web application security issues. The lack of available patches at the time of publication necessitates immediate mitigation efforts by affected organizations.

For European organizations, this vulnerability poses a risk primarily to confidentiality and integrity of user sessions and data. Attackers exploiting this XSS flaw can execute arbitrary scripts in the context of authenticated users, potentially stealing session cookies, redirecting users to malicious sites, or manipulating shared content. This can lead to unauthorized access to sensitive information or disruption of collaboration workflows. Organizations relying on FileCodeBox for code sharing or collaborative editing are particularly vulnerable. The impact is heightened in sectors with strict data protection requirements, such as finance, healthcare, and government, where leakage of sensitive data could result in regulatory penalties and reputational damage. Although availability is not directly impacted, the indirect effects of compromised user trust and potential data breaches can be significant. The medium severity score reflects the need for timely remediation but indicates that exploitation requires user interaction and some level of privilege, somewhat limiting the attack surface.

1. Monitor FileCodeBox vendor communications closely and apply security patches immediately upon release to address this vulnerability. 2. Until patches are available, restrict or disable the text sharing feature or limit its use to trusted users only. 3. Implement strict input validation and sanitization on all user-supplied data within the application to prevent injection of malicious scripts. 4. Deploy Content Security Policy (CSP) headers to restrict execution of unauthorized scripts in browsers accessing the application. 5. Educate users on the risks of clicking untrusted links or entering share codes from unknown sources. 6. Conduct regular security assessments and penetration testing focused on web application vulnerabilities, including XSS. 7. Use web application firewalls (WAFs) configured to detect and block common XSS attack patterns targeting FileCodeBox endpoints. 8. Review and limit user privileges within FileCodeBox to minimize the impact of compromised accounts. 9. Log and monitor access to shared codeboxes for unusual activity that may indicate exploitation attempts.