CVE-2021-36788 in yoast_seo Extension
Summary
by MITRE • 08/14/2021
The yoast_seo (aka Yoast SEO) extension before 7.2.3 for TYPO3 allows XSS.
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Analysis
by VulDB Data Team • 08/18/2021
The CVE-2021-36788 vulnerability represents a cross-site scripting flaw within the Yoast SEO extension for TYPO3 content management system. This vulnerability specifically affects versions prior to 7.2.3 and exposes the system to potential malicious code injection attacks. The Yoast SEO extension is widely used for search engine optimization purposes within TYPO3 environments, making this vulnerability particularly concerning for organizations that rely on the platform for their web presence. The flaw exists in how the extension handles user input and renders output within the TYPO3 administrative interface, creating an avenue for attackers to execute malicious scripts in the context of a victim's browser session.
The technical nature of this vulnerability stems from inadequate input sanitization and output encoding within the Yoast SEO extension's administrative components. When administrators or users interact with the extension's interface, improperly validated user-supplied data is directly rendered without proper HTML escaping or sanitization. This creates a classic XSS attack vector where malicious actors can inject script code through form fields, parameters, or other user-controllable inputs. The vulnerability falls under CWE-79 which specifically addresses Cross-Site Scripting flaws, and aligns with ATT&CK technique T1203 for Exploitation for Execution, where adversaries leverage web application vulnerabilities to execute malicious code.
The operational impact of this vulnerability extends beyond simple script execution, as successful exploitation could allow attackers to steal administrative credentials, modify content, redirect users to malicious sites, or perform actions with elevated privileges within the TYPO3 system. Given that the Yoast SEO extension is commonly used for managing SEO metadata, search terms, and content optimization parameters, attackers could potentially manipulate these settings to compromise the entire website's integrity. The vulnerability is particularly dangerous in environments where multiple administrators have access to the TYPO3 backend, as it could enable privilege escalation or persistent malicious presence within the system.
Organizations affected by this vulnerability should immediately upgrade to version 7.2.3 or later of the Yoast SEO extension to remediate the XSS vulnerability. System administrators should also implement additional security measures such as input validation at multiple layers, regular security scanning of web applications, and monitoring for suspicious administrative activities. The mitigation strategy should include implementing Content Security Policy headers to prevent unauthorized script execution, conducting comprehensive security audits of all installed TYPO3 extensions, and ensuring proper access controls are in place for administrative interfaces. Additionally, organizations should consider implementing web application firewalls and regular penetration testing to identify similar vulnerabilities that may exist in other components of their TYPO3 installations.