In November 2023, security researchers uncovered a disturbing vulnerability in the Live Preview for Contact Form 7 WordPress plugin, tracked as CVE-2023-47830. The security flaw? *Missing authorization checks*—a basic but critical oversight that could let any user, even those without privileges, exploit functions meant strictly for administrators.

Read on as we break down what happened, how bad actors could exploit this, and—if you own a vulnerable site—how to patch things up fast.

What’s the “Live Preview for Contact Form 7” Plugin?

The plugin lets WordPress admins and designers see a real-time preview of contact forms built with Contact Form 7. It’s handy for tweaking design—but that usefulness became a liability when security controls didn’t limit who could call powerful backend functions.

The Vulnerability in Simple Terms

CVE-2023-47830 is all about *missing authorization*. Certain functions in the plugin (versions up to and including 1.2.) let users preview or manipulate forms *without checking if the person making the call is actually an admin*.

Technical Breakdown

In WordPress plugins, admin actions should be limited with current_user_can() checks or nonces. But in vulnerable versions, some AJAX hooks expose “preview” and even “save” actions to *any logged-in user*—or in some cases, to anyone on the internet!

Here’s a simplified pseudocode with the problem

// Vulnerable code from the plugin:
add_action( 'wp_ajax_preview_cf7', 'preview_cf7_callback' );

function preview_cf7_callback() {
    // MISSING: check if current user is admin!
    // MISSING: nonce verification!
    $form_id = $_POST['form_id'];
    $contents = get_post( $form_id );
    echo $contents;
    wp_die();
}

At minimum, like this

function preview_cf7_callback() {
    if ( ! current_user_can( 'manage_options' ) ) {
        wp_die( 'Permission denied' );
    }
    // Nonce check would be even better.
    // ...rest of code...
}

Using a tool like curl or Burp Suite, send a request to the admin-ajax.php endpoint.

curl -d "action=preview_cf7&form_id=1234" \

https://victim.com/wp-admin/admin-ajax.php

Attacker Reads Protected Form Data

The endpoint could leak unpublished or sensitive info in forms. Similar access sometimes allows overwriting or deleting form data if other actions are unprotected.

If you want to check your own site, here’s a safe (read-only) proof-of-concept

curl -d "action=preview_cf7&form_id=1" \
     https://your-site.com/wp-admin/admin-ajax.php

If you receive form contents (not “Permission Denied”), you are vulnerable.

All versions through 1.2.

- At time of writing, the developer has released fixes in later versions

References

- WPScan Advisory: CVE-2023-47830
- Plugin Details at WordPress.org
- CVE database entry

Update the Plugin

Install the latest fixed version from here.

Conclusion

CVE-2023-47830 is a perfect example of *why* every single admin-level AJAX action *must* check user permissions. If you use “Live Preview for Contact Form 7,” update right now. Don’t let a simple oversight become the open door for your next breach.

Stay safe, and keep your plugins updated!

*If you found this helpful, share with your WordPress admin friends. The more who know, the stronger the web!*

Timeline

Published on: 12/09/2024 13:15:31 UTC