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

MITRE NVD CVE.ORG JSON API Print: PDF PDF

Summary

CVECVE-2026-1781
StatePUBLISHED
AssignerWordfence
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-03-11 02:16:03 UTC
Updated2026-04-22 21:27:27 UTC
DescriptionThe 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).

Risk And Classification

Primary CVSS: v3.1 6.5 MEDIUM from [email protected]

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

EPSS: 0.000720000 probability, percentile 0.220080000 (date 2026-04-22)

Problem Types: CWE-862 | CWE-862 CWE-862 Missing Authorization

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
3.1CNADECLARED6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
Low

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Dvankooten MC4WP Mailchimp For WordPress affected 4.11.1 semver Not specified

References

ReferenceSourceLinkTags
github.com/ibericode/mailchimp-for-wordpress/commit/5fdebc2a5e22d11287d0... [email protected] github.com
plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-for... [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-for... [email protected] plugins.trac.wordpress.org
cwe.mitre.org/data/definitions/862.html [email protected] cwe.mitre.org
plugins.trac.wordpress.org/changeset [email protected] plugins.trac.wordpress.org
plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-for... [email protected] plugins.trac.wordpress.org
www.wordfence.com/threat-intel/vulnerabilities/id/10262aa9-5656-4a2b-aeb5-06001... [email protected] www.wordfence.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Sarawut Poolkhet (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-02-03T12:30:59.000ZVendor Notified
CNA2026-03-10T13:11:15.000ZDisclosed
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