CVE-2026-65048 in Ninja Forms Plugin
Summary
by MITRE • 07/21/2026
Ninja Forms plugin for WordPress versions 3.10.4 through 3.14.9 contains an unauthenticated stored cross-site scripting vulnerability in the Repeatable Fieldset feature where parseSubmissionIndex() accepts arbitrary strings as submission indexes without numeric validation, and admin_form_element() interpolates the index directly into HTML without escaping. An unauthenticated attacker can submit a public form with a crafted repeater child key containing malicious script payloads, which execute in an administrator's browser when viewing submissions in the WordPress admin panel, enabling session-cookie theft, creation of administrator accounts, installation of malicious plugins, and arbitrary modification of site content.
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Analysis
by VulDB Data Team • 07/21/2026
The vulnerability under discussion affects the Ninja Forms plugin for WordPress, specifically versions ranging from 3.10.4 through 3.14.9, and represents a critical unauthenticated stored cross-site scripting flaw within the Repeatable Fieldset feature. This security weakness stems from inadequate input validation and improper output escaping mechanisms that collectively create a dangerous condition for administrative users. The vulnerability manifests when an attacker exploits the parseSubmissionIndex() function which accepts arbitrary strings as submission indexes without performing necessary numeric validation checks.
The technical implementation of this flaw occurs within the admin_form_element() function where the unvalidated index value gets directly interpolated into HTML output without proper escaping or sanitization. This direct interpolation creates a classic XSS vector that allows malicious script payloads to execute within the context of an administrator's browser session. The vulnerability is particularly dangerous because it operates as a stored XSS attack, meaning the malicious payload persists in the system and executes every time an administrator views affected submissions in the WordPress admin panel.
The operational impact of this vulnerability extends far beyond simple script execution, creating multiple attack vectors for threat actors seeking to compromise WordPress installations. When an administrator accesses the submissions page containing the maliciously crafted repeater field data, their browser executes the embedded scripts, potentially leading to complete session hijacking through cookie theft. Attackers could leverage this vulnerability to establish persistent administrative access by creating new administrator accounts, installing malicious plugins, or modifying existing site content to redirect traffic or exfiltrate sensitive data.
The security implications align with CWE-79 which specifically addresses cross-site scripting vulnerabilities in web applications, and follows patterns commonly referenced in ATT&CK framework under T1059 for command and control through scripting. This vulnerability demonstrates how seemingly minor input validation gaps can create significant security risks when combined with improper output handling practices. The attack requires no authentication to initiate, making it particularly attractive to threat actors seeking to exploit WordPress installations at scale.
Mitigation strategies should focus on immediate patching of affected Ninja Forms versions to the latest releases that contain proper input validation and output escaping fixes. Administrators should also implement additional security measures including restricting access to the WordPress admin panel through IP whitelisting, implementing web application firewalls, and conducting regular security audits of plugin installations. Regular monitoring of submission data for suspicious patterns and user access logs can help detect exploitation attempts, while multi-factor authentication implementation provides additional defense layers against session hijacking attacks that may result from successful XSS exploitation.