CVE-2026-15052
Received Received - Intake

Stored XSS in MailChimp Subscribe Forms WordPress Plugin

Publication date: 2026-08-01

Last updated on: 2026-08-01

Assigner: Wordfence

Description
The MailChimp Subscribe Form, Optin Builder, PopUp Builder, Form Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Form Field Values in all versions up to, and including, 4.3.3 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

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Meta Information

Published
2026-08-01
Last Modified
2026-08-01
Generated
2026-08-01
AI Q&A
2026-08-01
EPSS Evaluated
N/A
NVD
CVE-2026-15052
EUVD
EUVD-2026-51759

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
mailchimp subscribe_form to 4.3.3 (inc)
mailchimp optin_builder to 4.3.3 (inc)
mailchimp popup_builder to 4.3.3 (inc)
mailchimp form_builder to 4.3.3 (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 MailChimp Subscribe Form plugin for WordPress. It allows unauthenticated attackers to inject malicious scripts into form fields due to insufficient input sanitization and output escaping. These scripts execute when users access the affected pages.

Detection Guidance

This vulnerability can be detected by checking for outdated versions of the MailChimp Subscribe Form plugin. Use WordPress admin to verify the installed version or run a command like 'wp plugin list --name=mailchimp-subscribe-form' if using WP-CLI. Look for versions up to 4.3.3.

Impact Analysis

An attacker could steal user sessions, redirect users to malicious sites, or perform actions on their behalf. It may also lead to defacement of websites or unauthorized data access if the injected scripts are designed to exfiltrate sensitive information.

Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating GDPR's data protection principles or HIPAA's security requirements. Organizations may face compliance violations, fines, or reputational damage if exploited.

Mitigation Strategies

Update the MailChimp Subscribe Form, Optin Builder, PopUp Builder, Form Builder plugin for WordPress to the latest version, which is 4.3.3 or higher. If an update is not available, consider disabling or removing the plugin until a patch is released.

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