CVE-2026-1781Network attack vector

Unauthenticated subscription deletion via trusted action parameter

Published Mar 11, 2026 · Updated Mar 11, 2026

Missing authorization in MC4WP: Mailchimp for WordPress 4.11.1 and earlier allows remote attackers to unsubscribe arbitrary addresses. The form listener trusts the client-controlled _mc4wp_action POST value and routes unsubscribe submissions to Mailchimp without authorization. A publicly exposed form ID is sufficient to target an address in the connected Mailchimp audience, causing unauthorized subscription deletion.

CVSS severity6.5
Medium
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authorization in MC4WP: Mailchimp for WordPress 4.11.1 and earlier allows remote attackers to unsubscribe arbitrary addresses. The form listener trusts the client-controlled _mc4wp_action POST value and routes unsubscribe submissions to Mailchimp without authorization. A publicly exposed form ID is sufficient to target an address in the connected Mailchimp audience, causing unauthorized subscription deletion.

The record

CVE
CVE-2026-1781
Published
Mar 11, 2026
Updated
Mar 11, 2026
Vendor
ibericode
Product
MC4WP: Mailchimp for WordPress
Classifications
CWE-862, T1565.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=* <=4.11.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ibericode · MC4WP: Mailchimp for WordPressversion=* <=4.11.1

Published CVSS scores

6.5WordfenceCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-862Missing Authorization
T1565.001Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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