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CVE-2026-87917: MC4WP: Mailchimp for WordPress <= 4.14.0 - Reflected Cross-Site Scripting via 'data' Dynamic Content Tag

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-19 · updated 2026-09-21
• Weakness: CWE-79

Description

The MC4WP: Mailchimp for WordPress plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via 'data' Dynamic Content Tag in all versions up to, and including, 4.14.0 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link.

Affected products

• dvankooten MC4WP: Mailchimp for WordPress: through 4.14.0

References

• https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.14.0/includes/class-dynamic-content-tags.php#L127
• https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.14.0/includes/forms/class-form-tags.php#L109
• https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.14.0/includes/forms/class-form-tags.php#L57
• https://plugins.trac.wordpress.org/changeset?reponame=&new=3689679%40mailchimp-for-wp%2Ftags%2F4.14.1&old=3655905%40mailchimp-for-wp%2Ftags%2F4.14.0
• https://plugins.trac.wordpress.org/changeset?reponame=&new=3698084%40mailchimp-for-wp%2Ftags%2F4.14.1&old=3655905%40mailchimp-for-wp%2Ftags%2F4.14.0
• https://www.wordfence.com/threat-intel/vulnerabilities/id/ee4f837a-d0b5-48df-8c96-2a294985612e?source=cve

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