CVE-2026-4561
Received Received - Intake

Stored XSS in MC4WP Mailchimp for WordPress Plugin

Publication date: 2026-08-22

Last updated on: 2026-08-22

Assigner: Wordfence

Description
The MC4WP: Mailchimp for WordPress plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the form response message post meta fields (e.g., 'text_subscribed', 'text_error') in all versions up to, and including, 4.12.0 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with Author-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

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Meta Information

Published
2026-08-22
Last Modified
2026-08-22
Generated
2026-08-22
AI Q&A
2026-08-22
EPSS Evaluated
N/A
NVD
CVE-2026-4561
EUVD
EUVD-2026-64299

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
mc4wp mailchimp_for_wordpress to 4.12.0 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-79 The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

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Executive Summary

This vulnerability is a Stored Cross-Site Scripting (XSS) issue in the MC4WP: Mailchimp for WordPress plugin. It allows authenticated attackers with Author-level access or higher to inject malicious scripts into form response message fields. These scripts execute when users access the affected pages due to insufficient input sanitization and output escaping.

Detection Guidance

This vulnerability requires checking WordPress sites using the MC4WP plugin up to version 4.12.0. Inspect form response message post meta fields like 'text_subscribed' and 'text_error' for malicious scripts. Use WordPress admin dashboard or database queries to review these fields for unexpected JavaScript or HTML content.

Impact Analysis

An attacker could steal user sessions, redirect users to malicious sites, or perform actions on their behalf. It may also deface websites or spread malware. The impact depends on user privileges and the nature of the injected scripts.

Compliance Impact

This vulnerability could lead to data breaches, compromising user data and violating privacy regulations like GDPR or HIPAA. It may result in unauthorized access to sensitive information, leading to legal penalties and reputational damage.

Mitigation Strategies

Update the MC4WP plugin to the latest version immediately. If updating is not possible, disable the plugin temporarily. Review all form response messages in the database for signs of exploitation. Implement strict input validation for form fields and monitor for unauthorized changes.

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