CVE-2021-36827 in Ninja Forms Contact Form Plugin
Summary
by MITRE • 06/16/2022
Authenticated (admin or higher user role) Stored Cross-Site Scripting (XSS) vulnerability in Saturday Drive's Ninja Forms Contact Form plugin <= 3.6.9 at WordPress via "label".
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Analysis
by VulDB Data Team • 04/30/2025
This vulnerability exists within the Saturday Drive Ninja Forms Contact Form plugin for WordPress, specifically affecting versions 3.6.9 and earlier. The issue manifests as a stored cross-site scripting flaw that requires an authenticated user with administrator or higher privileges to exploit. The vulnerability is triggered through the "label" parameter, which is commonly used in form field configurations and user interface elements within the plugin's administrative interface.
The technical flaw occurs when administrators or privileged users input malicious script code into the label field of form elements. When other users view the form or related administrative pages, the stored script executes in their browser context, potentially leading to session hijacking, credential theft, or redirection to malicious sites. This represents a classic stored XSS vulnerability where the malicious payload is permanently stored on the server and executed whenever the affected page is accessed.
The operational impact of this vulnerability is significant for WordPress sites using the affected plugin version. An attacker with administrator access can craft malicious scripts that will execute in the browsers of other users, including site visitors, editors, or even other administrators. This could enable unauthorized access to sensitive data, modification of content, or complete compromise of the affected WordPress installation. The vulnerability is particularly dangerous because it requires only administrative privileges to exploit, which are often more limited than full system access but still provide substantial control over the website's functionality.
The vulnerability aligns with CWE-79 which classifies cross-site scripting as a critical web application security weakness, specifically addressing the improper validation or sanitization of user-provided input. From an ATT&CK framework perspective, this vulnerability maps to T1059.001 (Command and Scripting Interpreter: PowerShell) and T1566.001 (Phishing: Spearphishing Attachment) as it enables attackers to execute malicious scripts and potentially establish persistent access through compromised user sessions. The vulnerability also relates to T1588.002 (Resource Development: Malware) as it provides a vector for delivering malicious payloads to target users.
Mitigation strategies include immediately upgrading to the latest version of the Ninja Forms plugin where this vulnerability has been patched. Administrators should also implement proper input sanitization and output encoding practices, regularly audit user permissions, and monitor for unauthorized administrative activities. Additionally, implementing content security policies and using web application firewalls can provide additional protection layers against exploitation attempts. Regular security audits and penetration testing should be conducted to identify similar vulnerabilities in other plugins and themes that may be present in the WordPress ecosystem.