CVE-2021-24596 in youForms Plugin
Summary
by MITRE • 09/20/2021
The youForms for WordPress plugin through 1.0.5 does not sanitise escape the Button Text field of its Templates, allowing high privilege users (editors and admins) to perform Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed
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Analysis
by VulDB Data Team • 09/29/2021
The CVE-2021-24596 vulnerability affects the youForms WordPress plugin version 1.0.5 and earlier, representing a critical cross-site scripting weakness that undermines web application security. This vulnerability specifically targets the Button Text field within the plugin's Templates functionality, creating an attack vector that can be exploited by users with editor or administrator privileges. The flaw exists despite the WordPress installation's restriction of unfiltered_html capability, which typically prevents non-administrative users from injecting malicious scripts into the platform. The vulnerability demonstrates a failure in input validation and output escaping mechanisms within the plugin's codebase, allowing malicious payloads to persist in the system's template structure and execute when rendered in web browsers.
The technical nature of this vulnerability aligns with CWE-79 - Improper Neutralization of Input During Web Page Generation, which specifically addresses cross-site scripting issues occurring during the generation of web content. This weakness allows attackers to inject malicious scripts into web pages viewed by other users, potentially leading to session hijacking, data theft, or unauthorized administrative actions. The vulnerability operates through the plugin's template system where user input is not properly sanitized before being stored and subsequently rendered in web interfaces. Attackers with editor privileges can craft malicious Button Text values containing script tags or other malicious code that executes in the browsers of other users who view the affected forms or templates.
The operational impact of this vulnerability extends beyond simple script execution, as it enables attackers to leverage the elevated privileges of editors and administrators to perform more sophisticated attacks. When combined with other vulnerabilities or through social engineering, this XSS flaw could allow attackers to escalate privileges or gain access to sensitive administrative functions. The fact that the vulnerability persists even when unfiltered_html is disabled indicates a fundamental flaw in the plugin's security architecture, as it bypasses WordPress core security measures designed to prevent such attacks. This vulnerability essentially creates a backdoor for malicious actors to inject persistent scripts that can manipulate user sessions, steal cookies, or redirect users to malicious websites.
Organizations using the youForms plugin should immediately update to version 1.0.6 or later, which contains the necessary patches to address this vulnerability. System administrators should also implement additional monitoring to detect any suspicious template modifications or script injections in affected installations. The mitigation strategy should include reviewing all existing templates for malicious content and implementing proper input validation across all user-editable fields within the plugin. Security teams should consider implementing content security policies to further protect against potential exploitation of this vulnerability. This issue also highlights the importance of regular security audits of third-party plugins and the necessity of maintaining updated security practices even when core WordPress security features are properly configured. The vulnerability serves as a reminder that plugin developers must implement proper sanitization and escaping mechanisms for all user inputs to prevent XSS attacks that could compromise entire WordPress installations.