CVE-2025-26591 is a Stored Cross-Site Scripting (XSS) vulnerability identified in the WP fancybox plugin developed by Noor Alam for WordPress websites. This vulnerability arises due to improper neutralization of input during web page generation, classified under CWE-79. Specifically, the plugin fails to adequately sanitize or encode user-supplied input before rendering it on web pages, allowing malicious actors to inject and store arbitrary JavaScript code within the affected website's content. When other users or administrators access the compromised pages, the malicious script executes in their browsers within the context of the vulnerable site. The vulnerability affects all versions of WP fancybox up to and including version 1.0.4. 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) reveals that the attack can be launched remotely over the network with low attack complexity, requires low privileges, and user interaction is necessary (e.g., a user must visit a maliciously crafted page). The vulnerability impacts confidentiality, integrity, and availability to a limited extent, and the scope is changed, meaning the vulnerability affects components beyond the initially vulnerable component. No known exploits are currently reported in the wild, and no patches have been linked yet. Stored XSS vulnerabilities are particularly dangerous because they can lead to session hijacking, defacement, redirection to malicious sites, or distribution of malware, especially on websites with high user interaction or administrative access. Given that WP fancybox is a WordPress plugin used to display images and media in a fancybox overlay, this vulnerability could be exploited by injecting malicious scripts into image captions, descriptions, or other input fields processed by the plugin.

For European organizations, especially those operating websites using WordPress with the WP fancybox plugin, this vulnerability poses a significant risk. Exploitation could lead to unauthorized access to user sessions, theft of sensitive information such as login credentials or personal data, and potential defacement or disruption of web services. Organizations in sectors like e-commerce, government, healthcare, and finance, which rely heavily on WordPress-based content management systems, may face reputational damage and regulatory consequences under GDPR if personal data is compromised. The cross-site scripting vulnerability could also be leveraged for phishing campaigns targeting European users by injecting malicious scripts that mimic legitimate site content. Additionally, the vulnerability's ability to affect confidentiality, integrity, and availability, albeit at a limited level, means that attackers could manipulate website content or disrupt user interactions, impacting business continuity and trust. The requirement for low privileges and user interaction lowers the barrier for exploitation, increasing the likelihood of successful attacks if the vulnerability remains unpatched.

European organizations should take immediate steps to mitigate this vulnerability beyond generic patching advice. First, they should inventory all WordPress installations to identify instances of the WP fancybox plugin and verify the version in use. Since no official patch links are currently available, organizations should monitor vendor communications and trusted security advisories for updates or patches. In the interim, applying Web Application Firewall (WAF) rules specifically designed to detect and block XSS payloads targeting the plugin's input fields can reduce exploitation risk. Organizations should also implement strict Content Security Policy (CSP) headers to limit the execution of unauthorized scripts on their websites. Input validation and output encoding should be enforced at the application level where possible, including sanitizing user inputs that interact with the plugin. Regular security audits and penetration testing focusing on XSS vulnerabilities can help detect exploitation attempts. Additionally, educating website administrators and users about the risks of clicking on suspicious links or interacting with untrusted content can reduce the impact of user interaction requirements. Finally, organizations should prepare incident response plans to quickly address any exploitation attempts or breaches resulting from this vulnerability.