CVE-2026-4561

MC4WP: Mailchimp for WordPress <= 4.12.0 - Authenticated (Author+) Stored Cross-Site Scripting via Form Response Messages

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.

We have discovered 86,645 live websites that are affected by CVE-2026-4561.

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Affected Software

Product  MailChimp for WordPress
Category Marketing Automation
Vulnerable Domains86,645 live websites (55% of MailChimp for WordPress install base)
Vulnerable Versions
  • from 0 through 4.12
Vulnerable Versions Count124 versions ( 93% of all versions)


Common Weakness Enumeration

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')



Details

  • Published - Aug 22, 2026
  • Updated - Aug 24, 2026

Credits

  • Osvaldo Noe Gonzalez Del Rio (Os) (finder)

Website Distribution by Country

Number of websites using CVE-2026-4561
United States27,719 websites


Germany6,883 websites
GB5,823 websites
Italy4,890 websites
France4,508 websites
Netherlands2,521 websites
Spain2,393 websites
Canada2,125 websites
Australia1,905 websites
India1,588 websites

Website Distribution by TLD

Number of websites using CVE-2026-4561
.com39,793 websites
.org4,985 websites
.co.uk3,630 websites
.it3,310 websites
.de2,864 websites
.nl2,001 websites
.net1,696 websites
.com.au1,601 websites
.fr1,510 websites
.com.br1,367 websites

Vulnerable Versions

Vulnerable versions are highlighted in red

Websites affected by CVE-2026-4561

Top websites that are affected by CVE-2026-4561. Please click on the "Contact us" link to get more information.
DomainCountryRankContacts
*******.com United States*,***
****.org United States*,***
******.com United States*,***
********.com GB*,***
***************.***.au Australia**,***
*******.com United States**,***
******.com United States**,***
*********.com Switzerland**,***
***.me United States**,***
***********.com GB**,***
See full domain list

FAQ

CVE-2026-4561 is Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in MailChimp for WordPress
A total of 86,645 websites have been identified as vulnerable to CVE-2026-4561, based on global website indexing conducted by WebTechSurvey.
The MailChimp for WordPress is affected by the CVE-2026-4561 vulnerability.
MailChimp for WordPress versions up to and including 4.12 are vulnerable to CVE-2026-4561.