CVE-2021-24705 in NEX-Forms Plugin
Summary
by MITRE • 12/13/2021
The NEX-Forms WordPress plugin through 7.9.4 does not escape some of its settings and form fields before outputting them in attributes, which could allow high privilege users to perform Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed.
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Analysis
by VulDB Data Team • 12/16/2021
The vulnerability identified as CVE-2021-24705 affects the NEX-Forms WordPress plugin version 7.9.4 and earlier, representing a critical cross-site scripting flaw that undermines the security posture of affected WordPress installations. This vulnerability specifically targets the plugin's handling of user input within form fields and settings, where insufficient output escaping creates opportunities for malicious script injection. The flaw is particularly concerning because it allows users with high privilege levels to execute XSS attacks even when the WordPress installation has properly restricted the unfiltered_html capability, which typically prevents unescaped HTML content from being stored or displayed.
The technical implementation of this vulnerability stems from improper sanitization of user-provided data within the plugin's administrative interface and form rendering components. When administrators or privileged users create or modify forms using the NEX-Forms plugin, the input values are not adequately escaped before being embedded into HTML attributes or output contexts. This oversight creates multiple attack vectors where malicious scripts can be injected into form fields, settings configurations, or other user-controllable elements. The vulnerability manifests when the plugin outputs form data without sufficient HTML escaping mechanisms, allowing attackers to inject malicious JavaScript code that executes in the context of other users' browsers.
The operational impact of CVE-2021-24705 extends beyond simple XSS exploitation, as it represents a significant bypass of WordPress security controls that are designed to prevent privilege escalation and data compromise. Attackers with access to the WordPress admin panel or users with sufficient privileges can leverage this vulnerability to execute malicious scripts against other administrators or logged-in users who interact with the compromised forms. This creates a persistent threat where attackers can steal session cookies, perform unauthorized actions on behalf of other users, or redirect victims to malicious domains. The vulnerability's severity is amplified by the fact that it operates even when standard WordPress protections are in place, making it particularly dangerous for organizations that rely on proper capability management for security.
This vulnerability aligns with CWE-79, which describes Cross-Site Scripting flaws in software applications, and demonstrates how insufficient output escaping creates dangerous security gaps in web applications. The attack pattern follows typical XSS exploitation techniques where malicious input is stored and then executed in the browser context of other users, potentially leading to full account compromise or data exfiltration. From an ATT&CK framework perspective, this vulnerability maps to T1566.001 (Phishing via Social Media) and T1059.001 (Command and Scripting Interpreter), as attackers can use the XSS capability to deliver malicious payloads or establish persistent access through compromised user sessions. Organizations should prioritize patching this vulnerability immediately, as it provides attackers with a direct path to execute arbitrary code in the browser context of privileged users, potentially leading to complete system compromise. The remediation process requires updating to version 7.9.5 or later of the NEX-Forms plugin, where proper output escaping mechanisms have been implemented to prevent the injection of malicious content into HTML attributes and output contexts.