CVE-2026-25472 in Fusion Builder Plugin
Summary
by MITRE • 02/19/2026
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in ThemeFusion Fusion Builder fusion-builder allows Stored XSS.This issue affects Fusion Builder: from n/a through <= 3.14.3.
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Analysis
by VulDB Data Team • 02/22/2026
The vulnerability identified as CVE-2026-25472 represents a critical cross-site scripting flaw within the ThemeFusion Fusion Builder fusion-builder component, specifically impacting versions through 3.14.3. This weakness falls under the well-established CWE-79 category for improper neutralization of input during web page generation, creating a persistent security risk that enables attackers to inject malicious scripts into web pages viewed by other users. The vulnerability's classification as stored XSS indicates that malicious payloads are permanently stored on the server and executed whenever affected pages are accessed, making it particularly dangerous for content management systems and website builders that rely heavily on user-generated content. The flaw manifests when the fusion-builder component fails to properly sanitize or escape user input before rendering it within web page contexts, allowing attackers to craft malicious scripts that persist in the application's database or storage mechanisms.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the capability to hijack user sessions, steal sensitive information, manipulate website content, and potentially escalate privileges within the affected system. When users access pages that contain the stored malicious scripts, these payloads execute in the context of the victim's browser, enabling unauthorized actions such as cookie theft, redirection to malicious sites, or modification of website content. The attack vector typically involves an authenticated user with sufficient privileges to create or modify content within the fusion-builder interface, where input fields are not properly validated or sanitized before being saved to the database. This creates a persistent threat that can affect multiple users who subsequently view the compromised pages, making the vulnerability particularly concerning for websites with high user interaction or administrative capabilities.
Security professionals should consider this vulnerability in the context of the ATT&CK framework under the T1566 technique for initial access through social engineering, as attackers may exploit this weakness to deliver malicious payloads that can compromise user sessions. The vulnerability also aligns with T1071.004 for application layer protocol usage, as the malicious scripts may leverage HTTP/HTTPS protocols to communicate with attacker-controlled servers. Mitigation strategies must focus on implementing robust input validation and output encoding mechanisms throughout the fusion-builder component, ensuring that all user-supplied content undergoes proper sanitization before being stored or rendered. Organizations should prioritize immediate patching to versions beyond 3.14.3 where the vulnerability has been addressed, while also implementing additional security measures such as content security policies, regular security audits of user-generated content, and monitoring for suspicious activity within the fusion-builder interface. The remediation process should include comprehensive testing to verify that all input fields, including those in rich text editors and dynamic content areas, properly handle potentially malicious input without compromising functionality or user experience.
This vulnerability demonstrates the critical importance of maintaining secure coding practices in web application development, particularly when handling user input that may be rendered in browser contexts. The stored nature of the XSS attack means that even if immediate patching is not possible, administrators can implement temporary workarounds such as restricting user privileges, implementing web application firewalls, or manually sanitizing content before it reaches the affected system. Organizations should also consider implementing automated security scanning tools that can detect similar vulnerabilities in their web applications and establish regular security training for developers to prevent similar issues in future releases. The vulnerability serves as a reminder that even widely-used and seemingly stable components can harbor critical security flaws that require continuous monitoring and proactive security measures to protect against exploitation.