CVE-2025-6257 is a stored Cross-Site Scripting (XSS) vulnerability identified in the Euro FxRef Currency Converter WordPress plugin developed by joostdekeijzer. This plugin is designed to provide currency conversion features using Euro foreign exchange reference rates. The vulnerability affects all versions up to and including 2.0.2. The root cause is insufficient input sanitization and output escaping on user-supplied attributes within the plugin's currency shortcode functionality. Specifically, authenticated users with contributor-level privileges or higher can inject arbitrary JavaScript code into pages via the shortcode parameters. Because this is a stored XSS, the malicious script is saved in the WordPress database and executed in the browsers of any users who visit the compromised pages. The vulnerability does not require user interaction beyond visiting the affected page and does not require elevated privileges beyond contributor access. The CVSS 3.1 base score is 6.4 (medium severity), with vector AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N, indicating network exploitability, low attack complexity, privileges required at the contributor level, no user interaction needed, scope change, and low impact on confidentiality and integrity, with no impact on availability. No public exploits are currently known in the wild, and no official patches have been released at the time of publication (June 20, 2025).

For European organizations, this vulnerability poses a moderate risk primarily to websites using the Euro FxRef Currency Converter plugin on WordPress. Since the plugin is focused on Euro currency conversion, it is likely popular among European businesses, financial institutions, e-commerce platforms, and informational sites dealing with currency data. Exploitation could lead to the injection of malicious scripts that execute in the browsers of site visitors, potentially enabling session hijacking, credential theft, defacement, or redirection to malicious sites. The scope change in the CVSS vector indicates that the vulnerability can affect components beyond the initially vulnerable plugin, potentially compromising the integrity and confidentiality of user data across the site. Although availability is not impacted, the reputational damage and potential data breaches could be significant. The requirement for contributor-level access limits the attack surface to insiders or compromised accounts, but given that contributor roles are common in content management workflows, the risk remains notable. The absence of known exploits suggests limited active targeting currently, but the medium severity and ease of exploitation (no user interaction needed) warrant prompt attention. Organizations relying on this plugin should consider the risk of persistent XSS attacks that could affect both internal users and external visitors, especially in sectors with high regulatory scrutiny such as finance and e-commerce.

1. Immediate mitigation involves restricting contributor-level access strictly to trusted users and auditing existing user roles to prevent privilege escalation or account compromise. 2. Implement Web Application Firewall (WAF) rules to detect and block suspicious payloads targeting the currency shortcode parameters. 3. Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts on affected pages, reducing the impact of any injected scripts. 4. Regularly monitor website content and database entries for unexpected script tags or suspicious shortcode attributes. 5. Until an official patch is released, consider disabling or removing the Euro FxRef Currency Converter plugin if it is not critical to business operations. 6. For sites requiring the plugin, apply manual code reviews and implement custom input sanitization and output escaping for shortcode attributes as a temporary fix. 7. Educate content contributors about the risks of injecting untrusted content and enforce strict content validation policies. 8. Maintain up-to-date backups to enable quick restoration in case of compromise. These steps go beyond generic advice by focusing on access control, proactive detection, and containment strategies tailored to the plugin's usage context.