WordPress security changelog
HIGH CVE-2026-15052 Received

MailChimp form values let visitors store JavaScript

MailChimp Subscribe Form through 4.3.3 does not adequately sanitize submitted form-field values or escape them when later rendered. An unauthenticated visitor can store a script payload that executes whenever another user, including an Administrator, views the affected page; the record does not disclose the field names, submission action or output context.

CVE / CNA score 7.2 CVSS 3.1 · security@wordfence.com
NVD score Pending NVD has not published its own CVSS assessment.
Component
MailChimp Subscribe Form, Optin Builder, PopUp Builder, Form Builder
Plugin slug
mailchimp-subscribe-sm
Affected
<= 4.3.3
Safe version
> 4.3.3
Published
Aug 01, 2026
Weakness
CWE-79 — Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

This CVE was published Aug 01, 2026 and is one of 5 known issues for this plugin.

What to do

Update, patch or deactivate.

Update to a corrected release after 4.3.3. Review stored form values for scripts or event handlers, remove confirmed payloads, and invalidate privileged sessions if affected pages were viewed.

A safe version is available, so updating to that version or later is the preferred remediation. If an immediate update is not practical, consider a targeted application patch or temporarily restricting the affected functionality.

Deactivate only when warranted by your risk profile, or when advised by your hosting provider in the limited circumstances where the vulnerability cannot otherwise be mitigated. If you’re unsure which action is appropriate, contact Fused or your hosting provider for guidance.

Source record

Technical 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.

CVE / CNA vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

References

Primary and upstream sources