---
id: CVE-2026-15052
title: >-
  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 saniti…
summary: >-
  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 saniti…
severity: high
cvss: 7.2
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N'
cwe:
  - CWE-79
published: '2026-08-01'
updated: '2026-08-01'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-15052'
references:
  - url: >-
      https://plugins.trac.wordpress.org/browser/mailchimp-subscribe-sm/tags/4.3.3/admin/classes/ajax-requests-class.php#L1224
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/mailchimp-subscribe-sm/tags/4.3.3/admin/classes/ajax-requests-class.php#L2311
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/mailchimp-subscribe-sm/tags/4.3.3/admin/classes/ajax-requests-class.php#L906
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/mailchimp-subscribe-sm/tags/4.3.3/integrations/form-builder-database/extension.php#L127
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/mailchimp-subscribe-sm/tags/4.3.3/integrations/form-builder-database/extension.php#L179
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/changeset?reponame=&old=3627272%40mailchimp-subscribe-sm&new=3627272%40mailchimp-subscribe-sm
    label: security@wordfence.com
  - url: >-
      https://www.wordfence.com/threat-intel/vulnerabilities/id/c3d2425e-69e5-4efe-bbc6-0ef121e74341?source=cve
    label: security@wordfence.com
tags:
  - nvd
epss: 0.00302
epssPercentile: 0.23124
ingestedAt: '2026-08-02T05:17:47.962Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.