Understanding and Securing the WordPress REST API

What is the WordPress REST API?

The WordPress REST API is a powerful feature that allows developers to interact with a WordPress site remotely. It provides a standardised way to manage site data and perform actions via HTTP requests. However, if not properly secured, the REST API can expose sensitive information, such as the list of users on your WordPress site.

Why Should You Secure the User List?

Securing the user list is essential to prevent unauthorised access, which could lead to security vulnerabilities like brute-force attacks, phishing, or other malicious activities. By restricting access to the wp-json/wp/v2/users/ endpoint, you can protect your site’s user data from being exposed to the public.

Steps to Secure the User List

1. Disable REST API for Unauthorised Users

• What it Does: This method restricts access to the REST API for users who are not logged in or lack the necessary permissions.
• How to Implement:
  • Access your theme’s functions.php file.
  • Add the following code to restrict REST API access:

function restrict_rest_api_access($result) {
    if (!is_user_logged_in()) {
        return new WP_Error('rest_cannot_access', __('Sorry, you are not allowed to list users.'), array('status' => 401));
    }
    if (!current_user_can('list_users')) {
        return new WP_Error('rest_cannot_access', __('Sorry, you are not allowed to list users.'), array('status' => 403));
    }
    return $result;
}
add_filter('rest_authentication_errors', 'restrict_rest_api_access');

• Result: Unauthorised users will receive an error message when attempting to access the user list.

2. Remove User Endpoint from REST API

• What it Does: This method completely removes the user list endpoint from the REST API.
• How to Implement:
  • Add the following code to your theme’s functions.php file:

function remove_user_endpoints($endpoints) {
    if (isset($endpoints['/wp/v2/users'])) {
        unset($endpoints['/wp/v2/users']);
    }
    if (isset($endpoints['/wp/v2/users/(?P<id>[\d]+)'])) {
        unset($endpoints['/wp/v2/users/(?P<id>[\d]+)']);
    }
    return $endpoints;
}
add_filter('rest_endpoints', 'remove_user_endpoints');

• Result: The user list endpoint will no longer be accessible via the REST API.

3. Use a Security Plugin

• What it Does: This method allows you to manage and restrict access to the REST API using a security plugin.
• How to Implement:
  • Install a reputable security plugin via the WordPress dashboard.
  • Navigate to the REST API settings within the plugin and disable or restrict access to the users’ endpoint.
• Result: Simplifies the process of securing the REST API without needing to modify code.

4. Check if wp-json/wp/v2/users/ is Exposed

Before implementing security measures, it’s important to check if the user list is currently exposed via the REST API.

How to Check

1. Manual Check via Browser:
   • Open your web browser.
   • Enter the following URL in the address bar: https://yourdomain.com/wp-json/wp/v2/users/ (replace yourdomain.com with your actual domain).
   • If the user list is exposed, you will see a JSON response containing user data, including usernames and IDs. If it’s not exposed, you may receive an error message such as “Sorry, you are not allowed to list users.”
2. Use an Online Tool:
   • Several online tools can check for exposed REST API endpoints. Simply enter your website URL, and the tool will scan for open endpoints and report any exposed data.
3. Inspect REST API Endpoints Using a Plugin:
   • You can install a security plugin that provides insights into your site’s REST API endpoints. These plugins often include features that allow you to scan and review any publicly accessible data.

Result

If you find that the user list is exposed, it is crucial to implement one of the security measures outlined in this guide immediately. If the endpoint is not exposed, you should still consider implementing security practices to prevent future vulnerabilities.

In-Depth Guide: Understanding and Securing the WordPress REST API

Overview of the WordPress REST API

The WordPress REST API is a core feature that enables developers to interact with WordPress sites using HTTP requests. It allows for the creation, reading, updating, and deletion of resources such as posts, pages, and users. By default, the REST API is enabled for all WordPress sites, making it a versatile tool for developers.

However, this flexibility comes with potential risks. One such risk is the exposure of the user list through the wp-json/wp/v2/users/ endpoint. Without proper security measures, this data can be accessed by anyone, posing a threat to the site’s security.

Disabling REST API for Unauthorised Users

One of the most effective ways to secure the user list is by restricting access to the REST API for unauthorised users. This involves adding custom code to your WordPress site to ensure that only logged-in users with the appropriate permissions can access the API.

How It Works

The code provided checks if the user is logged in and whether they have the list_users capability. If these conditions are not met, the API request is denied with an error message. This method is highly effective for sites that require REST API functionality for specific users but want to restrict access for others.

Example Scenario

Consider a membership site where only administrators and editors need to access user data. By implementing this code, you ensure that only these user roles can access the API endpoint, protecting the user list from unauthorised viewing.

Removing the User Endpoint from REST API

If your site does not require the user list to be accessible via the REST API, you can remove the endpoint altogether. This approach is ideal for sites that do not use the REST API for user management or do not want any user data exposed through the API.

How It Works

The provided code removes the user-related endpoints from the REST API. This means that any attempts to access wp-json/wp/v2/users/ will result in a 404 error, effectively hiding the user list from potential threats.

Example Scenario

For a blog or informational site where user interaction is minimal, removing the user endpoint from the REST API can provide an additional layer of security without affecting the site’s functionality.

Using a Security Plugin to Manage REST API Access

For users who prefer not to modify code directly, using a security plugin is a convenient alternative. Many security plugins offer options to manage REST API access, allowing you to disable or restrict endpoints with just a few clicks.

How It Works

Once the plugin is installed, you can navigate to the REST API settings and configure access controls. This method is particularly useful for non-technical users who want to secure their site without delving into the technical details.

Example Scenario

An e-commerce site might use a security plugin to manage REST API access, ensuring that customer data is protected while still allowing necessary API functions for payment gateways and shipping providers.

How to Check if wp-json/wp/v2/users/ is Exposed

Ensuring your user list is secure involves checking if the REST API endpoint is currently accessible. This step is critical before applying further security measures.

Manual Check via Browser

You can easily check if the user list is exposed by directly accessing the API endpoint in your browser. Simply replace yourdomain.com with your actual domain in the following URL and enter it into your browser:

https://yourdomain.com/wp-json/wp/v2/users

If the user list is exposed, the browser will display a JSON response containing user data such as usernames and IDs. If it is not exposed, you will either see an error message or a blank response, indicating that the endpoint is secure.

Using Online Tools

Several online tools are available that can scan your website for exposed REST API endpoints. These tools analyse your site’s security and report any vulnerabilities, including the exposure of user data through the REST API.

Inspect REST API Endpoints with Plugins

For a more detailed inspection, consider using a WordPress plugin designed to monitor and control REST API endpoints. These plugins provide an overview of all accessible endpoints and help you identify any that might expose sensitive information.

What to Do if the User List is Exposed

If you find that your user list is accessible through the REST API, it’s important to take immediate action by implementing one of the security methods outlined above. This will prevent unauthorised users from accessing sensitive information and protect your site from potential security threats.

Additional Resources

For further information on securing your WordPress site and the REST API, visit the official WordPress documentation here.

Frequently Asked Questions (FAQ)

1. Why is the REST API enabled by default on WordPress?

• The REST API is enabled by default to provide a standardised method for developers to interact with WordPress sites. It allows for easier integration with third-party services and applications.

2. Can I completely disable the REST API if I don’t need it?

• Yes, you can disable the REST API for non-authenticated users or completely if your site does not rely on it. However, be cautious as some plugins or themes might require REST API functionality.

3. Will disabling the user endpoint affect my site’s functionality?

• Disabling the user endpoint will only affect the ability to retrieve user data via the REST API. It will not affect other site functions unless they rely specifically on this API endpoint.

4. Is there a risk in using custom code to secure the REST API?

• While using custom code is generally safe if implemented correctly, there is always a risk of conflicts with other themes or plugins. It is recommended to test the code in a staging environment before applying it to a live site.

5. How can SmartHost assist with securing my WordPress site?

• SmartHost offers a range of services including WordPress hosting, WordPress Care Plans with management, and security. Our support team can assist with implementing the best practices to protect your site. Contact us for more information.