CVE-2025-62939 identifies a stored Cross-site Scripting (XSS) vulnerability in Joe Open Currency Converter versions up to 1.5.0. The vulnerability stems from improper neutralization of user-supplied input during web page generation, which allows attackers to inject malicious scripts that are persistently stored on the server and executed in the context of other users’ browsers when they access affected pages. This type of vulnerability can be exploited to steal sensitive information such as session cookies, perform unauthorized actions on behalf of authenticated users, or deliver malware. The CVSS 3.1 base score is 5.4, indicating medium severity, with an attack vector of network (remote exploitation), low attack complexity, requiring privileges (PR:L) and user interaction (UI:R). The scope is changed (S:C), meaning the vulnerability affects components beyond the initially vulnerable component. Confidentiality and integrity impacts are low, and availability is not affected. No public exploits have been reported yet. The vulnerability affects all versions up to and including 1.5.0, with no patch links currently available. The vulnerability was reserved on 2025-10-24 and published on 2025-10-27 by Patchstack. Stored XSS vulnerabilities are particularly dangerous because the malicious payload persists on the server, increasing the likelihood of multiple users being affected.

For European organizations, especially those in finance, e-commerce, or any sector relying on Joe Open Currency Converter, this vulnerability poses a risk of session hijacking, credential theft, and unauthorized actions performed under the guise of legitimate users. The stored nature of the XSS means that once injected, the malicious script can affect multiple users over time, potentially leading to data breaches or fraud. Confidentiality and integrity of user data are at risk, although availability is not impacted. The requirement for user interaction and privileges limits the ease of exploitation but does not eliminate risk, particularly in environments where users have elevated privileges or where social engineering can be used to trigger the vulnerability. The absence of known exploits in the wild currently reduces immediate risk but does not preclude future attacks. Organizations handling sensitive financial data or large user bases are particularly vulnerable to reputational damage and regulatory penalties under GDPR if such vulnerabilities lead to data compromise.

Organizations should monitor for official patches from Joe and apply them promptly once available. In the absence of patches, implement strict input validation on all user-supplied data to reject or sanitize potentially malicious content before storage. Employ context-aware output encoding to neutralize any injected scripts when rendering data in web pages. Deploy Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of XSS attacks. Conduct regular security audits and penetration testing focused on web application inputs and stored data. Educate users and administrators about the risks of XSS and the importance of cautious interaction with untrusted content. Consider implementing Web Application Firewalls (WAFs) with rules designed to detect and block XSS payloads targeting this application. Finally, review user privilege assignments to minimize the number of users with rights that could facilitate exploitation.