A critical cross-site scripting (XSS) vulnerability has been discovered in the popular Yoast SEO WordPress plugin, potentially putting over 5 million websites at risk of compromise. Security researcher Bassem Essam identified the flaw and reported it through the Wordfence Bug Bounty Program. The vulnerability, found in all Yoast SEO versions up to 22.5, stems from insufficient input sanitization and output escaping, allowing unauthenticated attackers to inject malicious scripts via the plugin’s URL parameters.
When an administrator clicks on a crafted URL, the malicious script executes in their browser session, enabling attackers to create rogue admin accounts, inject backdoors into theme and plugin files, redirect visitors to malicious sites, and gain full control over the WordPress site. The attack relies on tricking an administrator into clicking a malicious link, making user vigilance crucial.
Yoast has responded by releasing a patched version, 22.6, to address this critical security flaw. All websites using Yoast SEO are strongly urged to update to the latest version immediately. According to WordPress.org, the plugin is active on over 5 million installations, highlighting the widespread impact of this vulnerability.
In response, Wordfence has implemented firewall rules to protect its users from exploit attempts targeting this flaw. Bassem Essam was awarded a $563 bug bounty for his responsible disclosure. This incident emphasizes the importance of maintaining updated WordPress plugins and the vital role of bug bounty programs in identifying and mitigating security vulnerabilities. Website administrators should update their plugins and review their sites for any signs of suspicious activity to ensure security.
