---

Introduction

CVE-2022-3852 is a security vulnerability affecting the popular VR Calendar plugin for WordPress. This vulnerability, present in versions up to and including 2.3.3, exposes WordPress sites to serious risks if left unpatched. Attackers can exploit this weakness to delete or modify calendars and change critical plugin settings—all without authentication—by leveraging a classic web attack called Cross-Site Request Forgery (CSRF).

In this comprehensive post, we’ll break down what’s behind CVE-2022-3852, how it can be exploited, and how to protect your WordPress site. We’ll include simple code explanations, real-world scenarios, and links to official advisories and resources.

What is CSRF?

Cross-Site Request Forgery (CSRF) is an attack technique that tricks logged-in users into submitting actions they didn’t intend. On WordPress, if a plugin doesn’t properly validate security tokens (called “nonces”), attackers can craft malicious links or forms. When a privileged user (like an admin) clicks such a link or visits a compromised site, the attacker’s request executes with the user’s permissions.

How Does CVE-2022-3852 Work?

The VR Calendar plugin failed to check the required WordPress nonce on several actions. Instead, it trusted all incoming requests, even those coming from outside the expected WordPress context. This means malicious websites could trick admins into sending unauthorized requests—from deleting calendars to altering plugin settings—just by getting them to click a link or browse a page.

Technical Details and Exploit Example

Let's look at an example to see how an attacker might use this vulnerability.

The plugin includes code like this (simplified for demonstration)

// Example vulnerable code: deleting a calendar without nonce check
add_action('admin_post_delete_vrcalendar', 'delete_calendar');

function delete_calendar() {
    $calendar_id = $_POST['calendar_id'];
    // No nonce verification!
    if($calendar_id) {
        delete_calendar_data($calendar_id);
        wp_redirect(admin_url('admin.php?page=vr-calendar'));
        exit;
    }
}

Here, delete_calendar will run if the admin_post_delete_vrcalendar action is triggered, but no security nonce is checked.

The attacker may create a page with a hidden form like this

<form action="https://victims-wordpress-site.com/wp-admin/admin-post.php?action=delete_vrcalendar"; method="POST" id="csrf-form">
  <input type="hidden" name="calendar_id" value="1">
</form>
<script>
  document.getElementById('csrf-form').submit();
</script>

If the logged-in admin visits this malicious page, the browser automatically submits the form, deleting calendar ID 1 without any confirmation.

WordPress uses nonces to protect against CSRF. A typical secured form includes a line like this

wp_nonce_field('delete_calendar_action', 'delete_calendar_nonce');

Then, before deleting any data, the handler checks

if (!isset($_POST['delete_calendar_nonce']) || !wp_verify_nonce($_POST['delete_calendar_nonce'], 'delete_calendar_action')) {
    wp_die('Security check failed!');
}

But in VR Calendar versions <= 2.3.3, these steps were missing or done incorrectly on several sensitive actions.

Delete calendars: Lose important data, bookings, schedules.

- Modify calendars: Change events, prices, or availability, potentially affecting business operations.
- Change plugin settings: Switch payment options, email addresses, etc., leading to lost sales or data leaks.

Who Can Trigger The Attack?

- Any unauthenticated attacker – the only requirement is tricking a logged-in admin or user with plugin privileges to visit a malicious site or click a link.

Responsible Disclosure & References

This vulnerability was publicly disclosed in November 2022.

References

- Wordfence Advisory (Technical Details)
- WPScan Entry
- NVD Entry for CVE-2022-3852

Use a WordPress Security Plugin

- Tools like Wordfence or Sucuri can prevent common attacks.

Conclusion

CVE-2022-3852 is a textbook example of how missing nonces can lead to high-severity site takeovers—no hacking skills needed, just luring an admin to visit a malicious site. If you manage a WordPress site using the VR Calendar plugin, upgrade now, and always keep your plugins updated. Stay proactive, and you’ll keep your website—and your business—safe.


*Stay safe, keep your WordPress sites updated, and be wary of suspicious links!*

Timeline

Published on: 11/03/2022 18:15:00 UTC
Last modified on: 11/04/2022 15:48:00 UTC