XMLRPC in WordPress: A Security Risk You Should Disable

Introduction

In the world of WordPress security, there are several components that require careful consideration, and one such component is the xmlrpc.php file. Introduced in WordPress 3.5, XMLRPC was designed to provide remote access to WordPress functionality. While it served a purpose in the past, it has become a potential vulnerability in today's threat landscape. In this blog post, we will explore what XMLRPC stands for, its historical uses, and the risks it poses, particularly in relation to brute force attacks. We will also discuss why disabling XMLRPC is a crucial step towards enhancing your WordPress security.

What is XMLRPC and its Historical Uses?

XMLRPC stands for XML-RPC (Remote Procedure Call), which is a protocol that enables communication between different software applications using XML messages over a network. In the context of WordPress, xmlrpc.php is a file that allows remote access to the WordPress API, enabling users to perform various actions like publishing posts, managing comments, and more, using external tools and applications.

When XMLRPC was first introduced in WordPress 3.5, it brought significant advantages. It facilitated seamless integration with mobile applications, desktop clients, and other third-party services. Users could conveniently publish content, moderate comments, and perform administrative tasks remotely, which was especially useful for content creators and site managers on the go.

The Risk of Brute Force Attacks

Unfortunately, XMLRPC has also become a target for malicious actors, primarily due to its potential for exploitation in brute force attacks. A brute force attack is a method wherein an attacker systematically tries different combinations of usernames and passwords until they find the correct credentials to gain unauthorised access to a WordPress site.

XMLRPC can be leveraged by attackers to launch brute force attacks by repeatedly attempting to log in to a site using various username and password combinations. This method exploits the ability of xmlrpc.php to process login requests without the need for direct interaction with the WordPress login page. By exploiting this vulnerability, attackers can automate the process of attempting multiple login combinations rapidly, increasing the likelihood of successfully compromising a site's security.

One of the key reasons why using XMLRPC for brute force attacks poses a significant threat is its ability to bypass plugins designed to detect and block such attacks. Unlike traditional login attempts that go through the WordPress login screen, XMLRPC allows attackers to directly send login requests to the xmlrpc.php file without triggering the standard login mechanisms. This means that security plugins specifically configured to monitor and block brute force attacks on the WordPress login screen may be rendered ineffective against XMLRPC-based attacks. By bypassing these detection and blocking measures, attackers can launch relentless and automated login attempts, increasing their chances of successfully compromising a WordPress site's security. This highlights the critical need to disable XMLRPC or implement additional security measures to counter this bypassing vulnerability.

Why Should XMLRPC be Disabled?

Considering the security risks associated with XMLRPC, it is highly recommended to disable it unless you have a specific requirement for its functionality. Here are a few reasons why disabling XMLRPC can be beneficial:

1. Protection Against Brute Force Attacks: By disabling XMLRPC, you eliminate the potential entry point for brute force attacks. Without XMLRPC, attackers cannot exploit its functionality to perform automated login attempts, significantly reducing the risk to your site's security.
2. Reduced Server Load: Brute force attacks can put a significant strain on your server resources, potentially affecting site performance and availability. Disabling XMLRPC helps alleviate this burden by preventing malicious actors from overwhelming your site's login system with automated login requests.
3. Enhanced Privacy: XMLRPC can expose sensitive information about your site, such as user data and site configurations, to potential attackers. By disabling XMLRPC, you mitigate the risk of inadvertently leaking this information.
4. Better Plugin Compatibility: Some security plugins recommend or even require the deactivation of XMLRPC as a security best practice. By disabling it, you ensure better compatibility with such security plugins and can take full advantage of their protective features.

Disabling XMLRPC

Disabling XMLRPC in WordPress is a straightforward process that can be achieved by following a few simple steps. While there are plugins available to disable XMLRPC, if you prefer not to rely on additional plugins for this relatively minor task, you can disable it manually by adding a code snippet to your theme or child theme's functions.php file.

add_filter( 'xmlrpc_enabled', '__return_false' );

This code snippet disables XMLRPC functionality by filtering the 'xmlrpc_enabled' hook and returning false.

Once you have added the code snippet and saved the changes, XMLRPC will be effectively disabled on your WordPress site.

However, if you are unable to modify the theme or child theme's functions.php file due to restricted access or disabled features, you can opt for a plugin as an alternative solution. While using a plugin is perfectly valid, it may seem unnecessary to dedicate significant runtime resources for such a small task.

Keep in mind that manually adding the code snippet to disable XMLRPC is a lightweight and efficient approach. It accomplishes the core task performed by most XMLRPC Switch Off plugins available. However, in situations where modifying files within your WordPress site is not feasible, using a plugin becomes a convenient workaround to disable XMLRPC.

Choose the method that suits your preferences and site requirements, either by manually adding the code snippet or by utilising a plugin, to effectively disable XMLRPC and bolster your WordPress site's security.

Further Hardening with Cloudflare

In addition to disabling XMLRPC, another highly recommended approach to further enhance the security of your WordPress site is by utilising Cloudflare. Cloudflare offers a range of powerful security features, including their caching and Content Delivery Network (CDN), which can significantly improve website performance. Moreover, Cloudflare provides robust tools to bolster security, even on their free tier account.

One of the valuable security features offered by Cloudflare is the ability to block requests that specifically target the XMLRPC file within WordPress. By leveraging Cloudflare's security settings, you can configure rules to identify and block any requests attempting to access xmlrpc.php, thus adding an extra layer of protection to your site.

To enable this feature in Cloudflare, follow these steps:

1. Sign up for a Cloudflare account: If you haven't already, create an account on Cloudflare (https://www.cloudflare.com/) and add your website to your Cloudflare dashboard.
2. Configure DNS settings: Follow the prompts on Cloudflare to configure your website's DNS settings and switch your domain's nameservers to Cloudflare.
3. Access the Cloudflare dashboard: Once your website is set up on Cloudflare, log in to your Cloudflare account and access the dashboard for your website.
4. Navigate to the Firewall (WAF) settings: In the Cloudflare dashboard, navigate to the "Security" > “WAF” section.
5. Create a new rule: Under the "Custom Rules" tab, create a new rule by clicking on the "Create rule" button.
6. Configure the rule: In the rule configuration, specify the criteria for blocking requests to xmlrpc.php. For example, you can set the "URI Path" to "/xmlrpc.php" and choose the action to "Block" such requests.
7. Save the rule: Once you have configured the rule, save it to apply the changes.

By setting up this rule, Cloudflare will block any incoming requests to the xmlrpc.php file, effectively preventing potential attacks that target this vulnerability.

It is worth noting that Cloudflare offers various other security features like DDoS protection, Web Application Firewall (WAF), and IP reputation-based blocking, which can further enhance the security of your WordPress site. These features, combined with their caching and CDN capabilities, make Cloudflare a powerful tool for hardening the security and improving the overall performance of any website, including WordPress.

Conclusion

While xmlrpc.php in WordPress had its merits when it was introduced, its potential for abuse in brute force attacks has made it a significant security risk in today's landscape. Disabling xmlrpc.php is a crucial step towards fortifying your WordPress site's security, protecting it from potential unauthorised access and reducing the strain on your server resources. By prioritising security measures like disabling XMLRPC, you can enjoy a safer and more secure WordPress experience.