CVE-2026-102391 in JetFormBuilder Plugin
Summary
by MITRE • 09/30/2026
Unauthenticated Cross Site Scripting (XSS) in JetFormBuilder <= 3.6.5.4 versions.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 09/30/2026
The vulnerability identified as an unauthenticated cross-site scripting flaw within JetFormBuilder versions prior to or equal to 3.6.5.4 represents a significant security risk for websites utilizing this WordPress plugin. Cross-site scripting, commonly referred to as XSS, is a type of injection attack where malicious scripts are injected into otherwise benign and trusted web pages. In the specific context of JetFormBuilder, which allows users to create complex forms with various fields and submission handlers, the vulnerability arises from insufficient input validation or improper output encoding when processing form data. This flaw permits an attacker who does not need to authenticate as a user on the target site to inject malicious client-side scripts into web pages viewed by other users. The unauthenticated nature of this exploit is particularly concerning because it lowers the barrier for entry, allowing any internet user with knowledge of the vulnerability and access to the form submission endpoint to execute code without needing valid credentials or prior interaction with an administrator account.
From a technical perspective, the root cause typically involves the application accepting raw input from users through form fields such as text inputs, comments, or file metadata, and then rendering this data directly into HTML output without adequate sanitization. When a victim user visits a page containing content influenced by the malicious payload, their browser executes the injected script in the context of the vulnerable site's domain. This allows the attacker to bypass same-origin policy restrictions, which are designed to prevent one website from interacting with another. The impact can vary depending on the sophistication of the payload but generally includes session hijacking, where the attacker steals authentication cookies or tokens to impersonate legitimate users; keylogging, capturing sensitive information typed into forms such as passwords or credit card numbers; and defacement of the website's appearance by manipulating DOM elements. In severe cases, if combined with other vulnerabilities like CSRF token bypasses, it can lead to complete account takeover or further propagation within the network infrastructure.
This vulnerability aligns closely with CWE-79, which is classified as Improper Neutralization of Input During Web Page Generation, commonly known as Cross-site Scripting. The lack of authentication required for exploitation places this flaw in a high-severity category according to many scoring systems because it affects availability and integrity without requiring privileged access. In terms of the MITRE ATT&CK framework, this activity maps to techniques under the Execution and Collection tactics, specifically T1059 which covers Command Line Interface or Scripting Interpreter execution via browser-based mechanisms, and potentially T1204 if used for initial user interaction leading to malware delivery. The unauthenticated aspect also relates to CWE-862, Missing Authorization, although in this specific XSS context, the primary failure is input validation rather than access control logic per se, but it effectively allows unauthorized actors to influence client-side behavior.
Mitigation strategies must be implemented both immediately and long-term to address this risk. The most critical step is upgrading JetFormBuilder to a version newer than 3.6.5.4 where the vendor has presumably patched the input handling mechanisms. For organizations unable to upgrade immediately, implementing Web Application Firewall rules can help detect and block common XSS payloads by filtering out suspicious characters such as angle brackets, quotes, and script tags in form submissions. Additionally, developers should ensure that all dynamic content is properly encoded using context-aware encoding techniques before being rendered in HTML, JavaScript, or CSS contexts. Enabling Content Security Policy headers on the web server can also mitigate the impact of successful XSS attacks by restricting the sources from which scripts are allowed to load and execute, thereby preventing inline script execution even if an injection occurs. Regular security audits and penetration testing focusing on form handling logic are recommended to identify similar weaknesses in other parts of the application ecosystem.