CVE-2024-4041: XSS Vulnerability in Yoast SEO Plugin

Bar Refael

May 9, 2024

A security vulnerability, designated as CVE-2024-4041, has been identified in the Yoast SEO plugin, which is actively used on over 5 million WordPress sites globally. This vulnerability arises from inadequate input sanitization and flawed output escaping mechanisms, particularly affecting the handling of URLs within the plugin’s architecture. The primary issue occurs in the add_premium_link() function within the WPSEO_Admin_Bar_Menu class and propagates to the build_shortlink() function in the WPSEO_Shortlinker class. The lapse in the escape function’s effectiveness allows unauthenticated attackers to deploy malicious scripts on affected websites.

Affected Software:

  • Plugin: Yoast SEO Plugin for WordPress
  • Active Installations: Over 5 million worldwide
  • Affected Assets: Yoast SEO <= 22.5
  • Classification: Reflected Cross-Site Scripting (XSS)
  • CVSS Score: 6.1 (Medium Severity)

Potential Impact:

Exploitation of this vulnerability can lead to arbitrary script execution triggered by user interactions, such as clicking compromised links. Potential outcomes include:

  • Unauthorized creation of administrative accounts
  • Injection of backdoors into the website’s infrastructure
  • Redirection of visitors to malevolent external URLs
  • Unauthorized access and potential data theft
  • Significant reputational damage for businesses relying on the integrity and availability of their web presence

Mitigation and Recommendations:

To address this security flaw, it is crucial for administrators of impacted sites to take immediate action:

  • Update Immediately: Upgrade the Yoast SEO plugin to the latest version as versions up to 22.5 are confirmed vulnerable.
  • Verify Link Sources: Carefully check the origin of links before engagement to prevent phishing and other exploits.
  • Educate Users: Raise awareness among site users and administrators about the risks associated with interacting with unknown or unsolicited links.

Additional Steps for Developers:

  • Developers and the web development community at large are urged to adopt comprehensive security protocols in software development cycles, especially for plugins that are widely utilized across numerous platforms.

Stay Secure. Stay Informed.

OP Innovate Research Team.

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