CVE-2025-13840 is a stored Cross-Site Scripting (XSS) vulnerability identified in the BUKAZU Search widget plugin for WordPress, affecting all versions up to and including 3.3.2. The vulnerability stems from improper neutralization of input during web page generation, specifically due to insufficient sanitization and output escaping of the 'shortcode' parameter within the 'bukazu_search' shortcode. Authenticated attackers with Contributor-level privileges or higher can exploit this flaw by injecting arbitrary JavaScript code into pages via the shortcode attribute. When other users access these compromised pages, the injected scripts execute in their browsers, potentially leading to session hijacking, privilege escalation, defacement, or unauthorized actions within the context of the victim's session. The vulnerability has a CVSS 3.1 base score of 6.4, indicating medium severity, with an attack vector of network, low attack complexity, requiring privileges (PR:L), no user interaction, and a scope change due to impact on other components. No public exploits have been reported yet, but the risk remains significant given the widespread use of WordPress and the common practice of allowing multiple contributors to publish content. The issue highlights the importance of proper input validation and output encoding in web applications, especially for user-supplied parameters that are rendered in HTML contexts. Since the vulnerability affects a plugin, the attack surface includes any WordPress site using the BUKAZU Search widget, which may be embedded in various themes and configurations. The vulnerability was published on December 12, 2025, and no official patches have been linked yet, emphasizing the need for immediate mitigation steps by site administrators.

For European organizations, this vulnerability poses a moderate risk primarily to websites running WordPress with the BUKAZU Search widget plugin installed. The ability for authenticated users with Contributor-level access to inject persistent malicious scripts can lead to compromise of user sessions, theft of sensitive information, and unauthorized actions performed on behalf of legitimate users. This can damage organizational reputation, lead to data breaches, and disrupt web services. Public-facing websites, especially those handling customer data or internal portals with multiple contributors, are at higher risk. The scope of impact includes confidentiality and integrity of user data, with no direct availability impact reported. Given the medium CVSS score and the requirement for authenticated access, the threat is more relevant to organizations with collaborative content management workflows. Additionally, the cross-site scripting vulnerability can be leveraged as a stepping stone for further attacks such as phishing or malware distribution. European organizations operating in sectors like e-commerce, media, education, and government, which often use WordPress extensively, should consider this a significant concern.

1. Immediately review and restrict Contributor-level and higher privileges to trusted users only, minimizing the risk of malicious shortcode injection. 2. Monitor and audit all shortcode usage in posts and pages for suspicious or unexpected script content. 3. Apply strict input validation and output escaping on the 'shortcode' parameter if custom code or overrides are used, ensuring no script tags or event handlers can be injected. 4. Disable or remove the BUKAZU Search widget plugin if it is not essential to the website’s functionality until an official patch is released. 5. Keep WordPress core and all plugins updated regularly and subscribe to vulnerability advisories for timely patching. 6. Employ Web Application Firewalls (WAF) with rules to detect and block common XSS payloads targeting shortcode parameters. 7. Educate content contributors about the risks of injecting untrusted content and enforce secure content publishing policies. 8. Conduct regular security scans and penetration tests focusing on plugin vulnerabilities and XSS vectors. 9. Once a patch is available from the vendor, prioritize its deployment across all affected systems. 10. Implement Content Security Policy (CSP) headers to reduce the impact of potential XSS exploitation by restricting script execution sources.