CVE-2017-16842 in Yoast SEO Plugin
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in admin/google_search_console/class-gsc-table.php in the Yoast SEO plugin before 5.8.0 for WordPress allows remote attackers to inject arbitrary web script or HTML.
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Analysis
by VulDB Data Team • 01/24/2021
The CVE-2017-16842 vulnerability represents a critical cross-site scripting flaw discovered in the Yoast SEO plugin for WordPress, specifically within the admin/google_search_console/class-gsc-table.php file. This vulnerability affected versions prior to 5.8.0 and posed significant security risks to WordPress websites utilizing the popular SEO plugin. The issue stems from inadequate input validation and output escaping mechanisms within the plugin's administrative interface, creating an exploitable condition that allows remote attackers to inject malicious scripts into the web application's response.
The technical flaw manifests when the plugin processes user-supplied input without proper sanitization before rendering it in the HTML output. Attackers can craft malicious payloads that get executed in the context of other users' browsers who visit the affected admin pages. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, specifically representing a stored XSS variant since the malicious content can be persisted and executed against multiple users. The vulnerability exists because the plugin fails to properly escape HTML characters in the data displayed within the Google Search Console table interface, allowing attackers to inject script tags or other malicious HTML elements that execute in the browser context of authenticated administrators.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to escalate privileges and gain unauthorized access to administrative functions. When administrators view the compromised plugin interface, their browsers execute the injected scripts, potentially allowing attackers to steal session cookies, perform actions on behalf of the administrator, or redirect users to malicious sites. This creates a significant risk for WordPress sites where the Yoast SEO plugin is installed, as administrators are typically high-privilege users with extensive access to site configuration and content management capabilities. The vulnerability is particularly dangerous because it operates within the admin interface, making it difficult to detect and potentially allowing attackers to maintain persistent access to compromised systems.
Mitigation strategies for CVE-2017-16842 primarily involve immediate patching of the affected Yoast SEO plugin to version 5.8.0 or later, which includes proper input sanitization and output escaping mechanisms. Organizations should also implement additional security measures such as input validation at multiple layers, content security policies to prevent script execution, and regular security audits of installed plugins. The vulnerability demonstrates the importance of proper secure coding practices including the principle of least privilege and defense in depth, as recommended by the ATT&CK framework for web application security. Administrators should also consider implementing web application firewalls and monitoring for suspicious activity patterns that might indicate exploitation attempts. Regular security updates and patch management processes are essential to prevent similar vulnerabilities from being exploited in the future, particularly given the widespread use of WordPress and its ecosystem of plugins.