Vulnerability-Lookup

GHSA-9VM9-FM4P-MCPM

Vulnerability from github – Published: 2026-03-11 03:31 – Updated: 2026-03-11 03:31

Details

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).

Severity

6.5 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

Show details on source website

JSON

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{
  "affected": [],
  "aliases": [
    "CVE-2026-1781"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-862"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-03-11T02:16:03Z",
    "severity": "MODERATE"
  },
  "details": "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).",
  "id": "GHSA-9vm9-fm4p-mcpm",
  "modified": "2026-03-11T03:31:27Z",
  "published": "2026-03-11T03:31:27Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-1781"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ibericode/mailchimp-for-wordpress/commit/5fdebc2a5e22d11287d011697a6b09331bd96fa5"
    },
    {
      "type": "WEB",
      "url": "https://cwe.mitre.org/data/definitions/862.html"
    },
    {
      "type": "WEB",
      "url": "https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form-listener.php#L207"
    },
    {
      "type": "WEB",
      "url": "https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form-listener.php#L53"
    },
    {
      "type": "WEB",
      "url": "https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form.php#L461"
    },
    {
      "type": "WEB",
      "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="
    },
    {
      "type": "WEB",
      "url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/10262aa9-5656-4a2b-aeb5-060018798369?source=cve"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-1781 (GCVE-0-2026-1781)

Vulnerability from cvelistv5 – Published: 2026-03-11 01:22 – Updated: 2026-04-08 16:35

Title

MC4WP: Mailchimp for WordPress <= 4.11.1 - Missing Authorization to Unauthenticated Arbitrary Subscription Deletion

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).

Severity

6.5 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-03-11 15:49 UTC

CWE

CWE-862 - Missing Authorization

Assigner

Wordfence CNA under the mitre root

CNA scorecard C 65/100 over 2294 records in the last 180 days details

References

7 references

URL	Tags
https://www.wordfence.com/threat-intel/vulnerabil…
https://plugins.trac.wordpress.org/browser/mailch…
https://plugins.trac.wordpress.org/browser/mailch…
https://plugins.trac.wordpress.org/browser/mailch…
https://cwe.mitre.org/data/definitions/862.html
https://github.com/ibericode/mailchimp-for-wordpr…
https://plugins.trac.wordpress.org/changeset?sfp_…

Impacted products

1 product

Vendor	Product	Version
dvankooten	MC4WP: Mailchimp for WordPress	Affected: 0 , ≤ 4.11.1 (semver)

Credits

Sarawut Poolkhet

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-1781",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-03-11T15:49:58.367011Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-03-11T15:50:08.687Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "MC4WP: Mailchimp for WordPress",
          "vendor": "dvankooten",
          "versions": [
            {
              "lessThanOrEqual": "4.11.1",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Sarawut Poolkhet"
        }
      ],
      "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)."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-862",
              "description": "CWE-862 Missing Authorization",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-08T16:35:55.094Z",
        "orgId": "b15e7b5b-3da4-40ae-a43c-f7aa60e62599",
        "shortName": "Wordfence"
      },
      "references": [
        {
          "url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/10262aa9-5656-4a2b-aeb5-060018798369?source=cve"
        },
        {
          "url": "https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form-listener.php#L53"
        },
        {
          "url": "https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form-listener.php#L207"
        },
        {
          "url": "https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form.php#L461"
        },
        {
          "url": "https://cwe.mitre.org/data/definitions/862.html"
        },
        {
          "url": "https://github.com/ibericode/mailchimp-for-wordpress/commit/5fdebc2a5e22d11287d011697a6b09331bd96fa5"
        },
        {
          "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="
        }
      ],
      "timeline": [
        {
          "lang": "en",
          "time": "2026-02-03T12:30:59.000Z",
          "value": "Vendor Notified"
        },
        {
          "lang": "en",
          "time": "2026-03-10T13:11:15.000Z",
          "value": "Disclosed"
        }
      ],
      "title": "MC4WP: Mailchimp for WordPress \u003c= 4.11.1 - Missing Authorization to Unauthenticated Arbitrary Subscription Deletion"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "b15e7b5b-3da4-40ae-a43c-f7aa60e62599",
    "assignerShortName": "Wordfence",
    "cveId": "CVE-2026-1781",
    "datePublished": "2026-03-11T01:22:03.740Z",
    "dateReserved": "2026-02-02T20:27:48.205Z",
    "dateUpdated": "2026-04-08T16:35:55.094Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Vulnerability timeline

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

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