The MC4WP: Mailchimp for WordPress plugin for WordPress is vulnerable to Stored Cross-Site Scripting via admin settings in all versions up to, and including, 4.9.16 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with administrator-level permissions and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This only affects multi-site installations and installations where unfilteredhtml has been disabled.

Missing Authorization vulnerability in ibericode MC4WP.This issue affects MC4WP: from n/a through 4.9.9.

URL Redirection to Untrusted Site ('Open Redirect') vulnerability in PluginOps MailChimp Subscribe Form, Optin Builder, PopUp Builder, Form Builder.This issue affects MailChimp Subscribe Form, Optin Builder, PopUp Builder, Form Builder: from n/a through 4.0.9.3.

The mailchimp-for-wp plugin before 4.1.8 for WordPress has XSS via the return value of addqueryarg.

The mailchimp-for-wp plugin before 4.0.11 for WordPress has XSS on the integration settings page.