WordPress Connect Contact Form 7 and Mailchimp Stored Cross-Site Scripting Vulnerability

A stored cross-site scripting vulnerability has been identified in the WordPress Connect Contact Form 7 and Mailchimp plugin, affecting all versions up to and including 0.9.78.06. The issue arises from inadequate input sanitization and output escaping, allowing unauthenticated attackers to inject arbitrary web scripts into pages. These scripts execute when a privileged user, such as an administrator, performs a contact lookup for the email address submitted via the Contact Form 7 form. This exploitation defers the execution of the injected script until an administrator interacts with the affected entry.

Impact

Exploitation of this vulnerability allows for stored cross-site scripting, where injected scripts are executed in the context of the user accessing the page.

Reproduction

To reproduce this vulnerability, an attacker can submit a form using the Contact Form 7 integration with Mailchimp, injecting a script into the Mailchimp merge field values. Once the form is submitted, an administrator can perform a contact lookup for the submitted email address, triggering the execution of the injected script.