CVE-2025-3597 is a medium-severity Cross-Site Scripting (XSS) vulnerability identified in the Firelight Lightbox WordPress plugin versions prior to 2.3.15. This vulnerability arises due to insufficient input sanitization when the jQuery Metadata library is enabled. The plugin allows users with post writing capabilities—typically authors or editors—to execute arbitrary JavaScript code. Although this feature was originally intended to be accessible only to users of the Pro version of the plugin, it can be activated in the free version as well, broadening the potential attack surface. The vulnerability leverages the ability of authorized users to inject malicious scripts that could be executed in the context of other users' browsers, potentially leading to session hijacking, privilege escalation, or the delivery of malicious payloads. The CVSS 3.1 base score of 5.9 reflects a medium severity, with an attack vector of network (remote exploitation), low attack complexity, requiring high privileges (post writing capability), and user interaction. The vulnerability impacts confidentiality, integrity, and availability to a limited extent, as exploitation requires authenticated users with specific roles and user interaction. No known exploits are currently reported in the wild, and no official patches have been linked yet, indicating that mitigation relies on plugin updates once available or alternative protective measures.

For European organizations, especially those relying on WordPress for content management and using the Firelight Lightbox plugin, this vulnerability poses a moderate risk. Attackers who gain or already have post writing privileges could exploit this flaw to inject malicious scripts, potentially compromising the security of site administrators, editors, or visitors. This could lead to unauthorized access to sensitive information, defacement, or distribution of malware. Organizations in sectors such as media, e-commerce, education, and government that maintain WordPress sites with collaborative content creation are particularly at risk. The impact is heightened in environments where user roles are not strictly managed or where multiple contributors have elevated privileges. Additionally, the vulnerability's ability to affect both free and Pro versions increases the likelihood of exposure. Given the interconnected nature of European digital infrastructure and the GDPR requirements for data protection, exploitation could also result in regulatory penalties if personal data is compromised.

1. Immediate mitigation should focus on restricting post writing capabilities to trusted users only, minimizing the number of users who can potentially exploit this vulnerability. 2. Disable or remove the jQuery Metadata library if it is not essential for site functionality, as this component is central to the vulnerability. 3. Monitor and audit user activities closely to detect any unusual script injections or content modifications. 4. Implement Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts within the WordPress environment. 5. Regularly update the Firelight Lightbox plugin to version 2.3.15 or later once available, as this will contain the official fix. 6. Employ Web Application Firewalls (WAFs) with rules tailored to detect and block XSS payloads targeting this plugin. 7. Educate users with post writing privileges about the risks of executing or embedding untrusted scripts. 8. Conduct periodic security assessments and penetration testing focusing on WordPress plugins and user privilege configurations.