FKIE_CVE-2026-1781

Vulnerability from fkie_nvd - Published: 2026-03-11 02:16 - Updated: 2026-04-22 21:27
Severity ?
6.5 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
Summary
The MC4WP: Mailchimp for WordPress plugin for WordPress is vulnerable to Missing Authorization in all versions up to, and including, 4.11.1. This is due to the plugin trusting the `_mc4wp_action` POST parameter without validation, allowing unauthenticated attackers to force the form to process unsubscribe actions instead of subscribe actions. This makes it possible for unauthenticated attackers to arbitrarily unsubscribe any email address from the connected Mailchimp audience via the `_mc4wp_action` parameter, granted they can obtain the form ID (which is publicly exposed in the HTML source).
References
security@wordfence.comhttps://cwe.mitre.org/data/definitions/862.html
security@wordfence.comhttps://github.com/ibericode/mailchimp-for-wordpress/commit/5fdebc2a5e22d11287d011697a6b09331bd96fa5
security@wordfence.comhttps://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form-listener.php#L207
security@wordfence.comhttps://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form-listener.php#L53
security@wordfence.comhttps://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form.php#L461
security@wordfence.comhttps://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&new=3477825%40mailchimp-for-wp%2Ftrunk&old=3443118%40mailchimp-for-wp%2Ftrunk&sfp_email=&sfph_mail=
security@wordfence.comhttps://www.wordfence.com/threat-intel/vulnerabilities/id/10262aa9-5656-4a2b-aeb5-060018798369?source=cve
Impacted products
Vendor Product Version
To clipboard 

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "The MC4WP: Mailchimp for WordPress plugin for WordPress is vulnerable to Missing Authorization in all versions up to, and including, 4.11.1. This is due to the plugin trusting the `_mc4wp_action` POST parameter without validation, allowing unauthenticated attackers to force the form to process unsubscribe actions instead of subscribe actions. This makes it possible for unauthenticated attackers to arbitrarily unsubscribe any email address from the connected Mailchimp audience via the `_mc4wp_action` parameter, granted they can obtain the form ID (which is publicly exposed in the HTML source)."
    },
    {
      "lang": "es",
      "value": "El plugin de WordPress MC4WP: Mailchimp for WordPress es vulnerable a la falta de autorizaci\u00f3n en todas las versiones hasta la 4.11.1, inclusive. Esto se debe a que el plugin conf\u00eda en el par\u00e1metro POST \u0027_mc4wp_action\u0027 sin validaci\u00f3n, lo que permite a atacantes no autenticados forzar al formulario a procesar acciones de desuscripci\u00f3n en lugar de acciones de suscripci\u00f3n. Esto hace posible que atacantes no autenticados desuscriban arbitrariamente cualquier direcci\u00f3n de correo electr\u00f3nico de la audiencia de Mailchimp conectada a trav\u00e9s del par\u00e1metro \u0027_mc4wp_action\u0027, siempre que puedan obtener el ID del formulario (que est\u00e1 expuesto p\u00fablicamente en el c\u00f3digo fuente HTML)."
    }
  ],
  "id": "CVE-2026-1781",
  "lastModified": "2026-04-22T21:27:27.950",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "LOW",
          "baseScore": 6.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 2.5,
        "source": "security@wordfence.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-03-11T02:16:03.493",
  "references": [
    {
      "source": "security@wordfence.com",
      "url": "https://cwe.mitre.org/data/definitions/862.html"
    },
    {
      "source": "security@wordfence.com",
      "url": "https://github.com/ibericode/mailchimp-for-wordpress/commit/5fdebc2a5e22d11287d011697a6b09331bd96fa5"
    },
    {
      "source": "security@wordfence.com",
      "url": "https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form-listener.php#L207"
    },
    {
      "source": "security@wordfence.com",
      "url": "https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form-listener.php#L53"
    },
    {
      "source": "security@wordfence.com",
      "url": "https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form.php#L461"
    },
    {
      "source": "security@wordfence.com",
      "url": "https://plugins.trac.wordpress.org/changeset?sfp_email=\u0026sfph_mail=\u0026reponame=\u0026new=3477825%40mailchimp-for-wp%2Ftrunk\u0026old=3443118%40mailchimp-for-wp%2Ftrunk\u0026sfp_email=\u0026sfph_mail="
    },
    {
      "source": "security@wordfence.com",
      "url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/10262aa9-5656-4a2b-aeb5-060018798369?source=cve"
    }
  ],
  "sourceIdentifier": "security@wordfence.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-862"
        }
      ],
      "source": "security@wordfence.com",
      "type": "Secondary"
    }
  ]
}


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