CVE-2019-20173 in Auth0 wp-auth0 Plugin
Summary
by MITRE
The Auth0 wp-auth0 plugin 3.11.x before 3.11.3 for WordPress allows XSS via a wle parameter associated with wp-login.php.
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Analysis
by VulDB Data Team • 05/10/2025
The Auth0 wp-auth0 plugin vulnerability identified as CVE-2019-20173 represents a critical cross-site scripting flaw that affects WordPress environments utilizing the Auth0 authentication plugin. This vulnerability specifically targets version 3.11.x prior to 3.11.3, creating a persistent security risk for WordPress sites that rely on this authentication framework. The issue manifests through improper input validation of the wle parameter within the wp-login.php endpoint, which serves as a critical authentication pathway for WordPress installations. The vulnerability falls under CWE-79 which categorizes cross-site scripting flaws, specifically representing a client-side injection vulnerability that enables attackers to execute malicious scripts within the victim's browser context. This flaw demonstrates how authentication plugins can inadvertently introduce security weaknesses into WordPress ecosystems, particularly when dealing with parameter handling in login workflows.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious URL containing a specially crafted wle parameter that gets processed by the wp-auth0 plugin without adequate sanitization or output encoding. When a victim navigates to such a crafted URL, the malicious script embedded within the wle parameter executes in the victim's browser context, potentially leading to session hijacking, credential theft, or other malicious activities. The vulnerability exploits the lack of proper input validation and output encoding mechanisms within the plugin's handling of the wle parameter, which is typically used for redirecting users after authentication. Attackers can leverage this weakness to inject malicious JavaScript code that persists across user sessions, making it particularly dangerous in environments where multiple users interact with the same WordPress installation. The attack vector specifically targets the WordPress login page which represents a high-value target due to its role in user authentication and access control.
The operational impact of this vulnerability extends beyond simple script execution, as it can lead to complete compromise of user sessions and potential privilege escalation within WordPress environments. When successful, attackers can hijack user sessions, steal authentication cookies, and potentially gain unauthorized access to administrative functions within WordPress. The vulnerability affects all WordPress installations using the affected plugin versions, regardless of the underlying WordPress version or other security measures in place. This makes it particularly dangerous as it can be exploited even in well-secured environments where other security controls might prevent traditional attack vectors. The persistence of the XSS flaw means that once exploited, attackers can maintain access to user sessions for extended periods, potentially allowing for data exfiltration, content manipulation, or further network exploitation. The vulnerability also impacts the integrity of the authentication process, potentially undermining trust in the entire WordPress authentication system.
Organizations should implement immediate mitigations including updating the wp-auth0 plugin to version 3.11.3 or later, which contains the necessary patches to address the input validation and output encoding issues. System administrators should also consider implementing additional security measures such as content security policies, web application firewalls, and regular security audits of installed plugins to identify similar vulnerabilities. The remediation process should include thorough testing of the updated plugin to ensure compatibility with existing WordPress configurations and authentication workflows. Security monitoring should be enhanced to detect unusual login patterns or suspicious URL parameters that might indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to T1566 (Phishing) and T1059 (Command and Scripting Interpreter) as attackers can use the XSS to deliver malicious payloads and maintain persistence. Organizations should also consider implementing automated patch management processes to ensure timely updates of third-party plugins and reduce the window of exposure to similar vulnerabilities. Regular security assessments of WordPress installations should include comprehensive plugin vulnerability scanning to identify and remediate similar issues before they can be exploited by malicious actors.