CVE-2024-3866 in Ninja Forms Plugin
Summary
by MITRE • 09/25/2024
The Ninja Forms Contact Form plugin for WordPress is vulnerable to Reflected Self-Based Cross-Site Scripting via the 'Referer' header in all versions up to, and including, 3.8.15 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link. Successful exploitation of this vulnerability requires "maintenance mode" for a targeted form to be enabled. However, there is no setting available to the attacker or even an administrator-level user to enable this mode. The mode is only enabled during a required update, which is a very short window of time. Additionally, because of the self-based nature of this vulnerability, attackers would have to rely on additional techniques to execute a supplied payload in the context of targeted user.
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Analysis
by VulDB Data Team • 03/09/2025
The vulnerability identified as CVE-2024-3866 affects the Ninja Forms Contact Form plugin for WordPress, representing a reflected self-based cross-site scripting flaw that exists in versions up to and including 3.8.15. This security weakness stems from inadequate input sanitization and insufficient output escaping mechanisms within the plugin's handling of the 'Referer' HTTP header. The vulnerability creates a dangerous condition where malicious actors can inject arbitrary web scripts into pages that will execute when unsuspecting users interact with compromised content. The attack vector specifically requires that maintenance mode be enabled for a targeted form, which presents a significant operational hurdle for exploitation attempts.
The technical implementation of this vulnerability demonstrates a classic reflected XSS pattern where the plugin fails to properly sanitize user-supplied input from the Referer header before rendering it in the web page context. This insufficient sanitization creates an opening for attackers to inject malicious scripts that can execute in the victim's browser context. The self-based nature of the vulnerability means that the malicious payload must be crafted to execute within the same context where it was injected, requiring additional attack techniques beyond simple payload delivery. The exploitation process becomes more complex because maintenance mode activation occurs only during required plugin updates, creating a very narrow time window for successful exploitation.
The operational impact of this vulnerability extends beyond simple script injection, as it can potentially enable more sophisticated attacks such as session hijacking, credential theft, or redirection to malicious sites. The requirement for maintenance mode to be active during a plugin update process significantly limits the window of opportunity for attackers, yet this constraint does not eliminate the threat entirely. The vulnerability's classification aligns with CWE-79, which addresses cross-site scripting flaws, and can be mapped to ATT&CK technique T1059.007 for script execution. Even though the maintenance mode activation is temporary, the potential for exploitation remains significant given that attackers could potentially manipulate update processes or exploit other vectors to trigger the vulnerable code path.
The security implications of this vulnerability are particularly concerning because it affects a widely used WordPress plugin with extensive deployment across various web environments. The fact that no direct setting exists for either attackers or administrators to enable maintenance mode adds complexity to both exploitation and mitigation strategies. However, the vulnerability's existence in all versions up to 3.8.15 indicates a persistent flaw that requires immediate attention. Organizations using Ninja Forms should prioritize updating to patched versions while implementing additional monitoring for unusual Referer header patterns. The vulnerability's remediation should focus on implementing proper input validation and output encoding mechanisms, particularly for HTTP headers that are commonly manipulated in web attacks, aligning with security best practices for preventing XSS vulnerabilities in web applications.