CVE-2025-49940 is a medium-severity DOM-based Cross-site Scripting (XSS) vulnerability found in ThemeFusion's Fusion Builder plugin for WordPress, affecting versions up to and including 3.13.2. The vulnerability stems from improper neutralization of input during web page generation, which allows malicious actors to inject and execute arbitrary JavaScript code within the context of the victim's browser. This type of XSS is DOM-based, meaning the malicious payload is executed as a result of client-side script processing, rather than server-side injection. The vulnerability requires the attacker to have at least low privileges (PR:L) and user interaction (UI:R), such as tricking a user into clicking a crafted link or interacting with malicious content. The attack complexity is low (AC:L), and the vulnerability affects confidentiality, integrity, and availability to a limited extent (C:L/I:L/A:L). The scope is changed (S:C), indicating that exploitation can affect resources beyond the vulnerable component. Although no known exploits are currently reported in the wild, the presence of this vulnerability in a popular WordPress page builder plugin poses a significant risk to websites using Fusion Builder, especially those with privileged users or administrators who can trigger the vulnerability. The vulnerability was reserved in June 2025 and published in October 2025, with no patch links currently available, indicating that remediation may still be pending or in progress. The CVSS vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L) highlights that the attack is network-based, requires low complexity, privileges, and user interaction, and impacts confidentiality, integrity, and availability at a low level but with scope change.

For European organizations, the impact of CVE-2025-49940 can be significant, particularly for those relying on WordPress websites that utilize the Fusion Builder plugin. Successful exploitation could allow attackers to execute arbitrary scripts in the context of users’ browsers, potentially leading to session hijacking, theft of sensitive information, unauthorized actions on behalf of users, or defacement of websites. This can damage organizational reputation, lead to data breaches involving personal or business-critical data, and disrupt web services. Given the medium severity and the requirement for user interaction and privileges, the threat is more pronounced in environments where multiple users have elevated access or where social engineering can be leveraged effectively. The scope change indicates that the impact could extend beyond the immediate vulnerable component, potentially affecting other integrated systems or services. European organizations in sectors such as e-commerce, media, education, and government that maintain public-facing WordPress sites are particularly at risk. Additionally, regulatory frameworks like GDPR impose strict data protection requirements, so exploitation leading to data leakage could result in legal and financial penalties.

1. Monitor ThemeFusion and official plugin repositories for patches addressing CVE-2025-49940 and apply them promptly once available. 2. Until patches are released, restrict Fusion Builder usage to trusted users only, minimizing the number of users with privileges that can trigger the vulnerability. 3. Implement strict input validation and sanitization on all user-supplied data that interacts with Fusion Builder components, especially those that influence DOM generation. 4. Deploy Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of potential XSS attacks. 5. Educate users and administrators about the risks of clicking on suspicious links or interacting with untrusted content to reduce the likelihood of successful social engineering. 6. Conduct regular security audits and penetration testing focused on web application vulnerabilities, including DOM-based XSS. 7. Consider isolating or sandboxing Fusion Builder components within the web application to limit scope and impact if exploited. 8. Review and tighten user privilege assignments within WordPress to follow the principle of least privilege, reducing the attack surface.