10 min read
WordPress remains one of the most popular content management systems in the world, but its XML-RPC interface presents a hidden vulnerability that attackers can exploit. From automated login attempts to distributed denial-of-service attacks, XML-RPC attacks pose serious risks to website stability and data integrity.
Fortunately, there are practical measures that can mitigate these threats, ranging from disabling unnecessary features to implementing advanced firewalls. In this guide, we will explore best practices for securing WordPress against XML-RPC attacks, ensuring both protection and peace of mind for site owners.
What is XML-RPC and how it worksLink to heading
XML-RPC, which stands for Extensible Markup Language Remote Procedure Call, is a protocol that allows communication between different systems over the internet. It enables one computer to execute commands or functions on another system by sending XML-formatted messages. XML-RPC acts as a bridge, allowing external applications and services to interact with the WordPress site, perform actions, and retrieve information remotely.
Within WordPress, XML-RPC provides critical functionality for mobile applications, desktop clients, and third-party services that need to interact with the website. For example, it allows posting content, editing pages, managing comments, or publishing media files remotely. XML-RPC also supports integration with external tools such as Jetpack, the WordPress mobile app, and other automation services, making it an essential component for remote site management and workflow automation.
Why XML-RPC Are a Security ConcernLink to heading
One of the primary concerns with XML-RPC in WordPress is its exposure of login mechanisms. Unlike the standard login page, XML-RPC can process multiple login attempts through a single request, which attackers can exploit. This feature makes it a prime target for brute-force attacks, as hackers can attempt thousands of username and password combinations without triggering traditional login attempt restrictions.
Beyond brute-force attacks, XML-RPC can also be leveraged for pingback-based DDoS attacks or other malicious activities that abuse the protocol to overwhelm server resources. Because XML-RPC is enabled by default in WordPress, attackers can remotely access its functions without direct authentication in some cases, particularly on outdated or misconfigured sites.
Common XML-RPC Attack MethodsLink to heading
Brute Force via XML-RPCLink to heading
Attackers frequently exploit the XML-RPC interface in WordPress to conduct brute force attacks, which involve systematically attempting multiple username and password combinations until a correct one is discovered. Unlike traditional login brute force attempts through wp-login.php, XML-RPC allows attackers to send multiple authentication requests within a single HTTP request, making it far more efficient and harder to detect.
This method can quickly overwhelm standard login security mechanisms and significantly increase the risk of unauthorized access, especially if administrators use weak or commonly used passwords.
Pingback-based DDoS attacksLink to heading
The XML-RPC pingback functionality, originally designed to notify other websites of linked content, can be maliciously leveraged to perform distributed denial-of-service (DDoS) attacks. Attackers exploit this feature by sending pingback requests that force multiple websites to unknowingly participate in a coordinated attack, thereby overloading the target server with traffic.
Real-world examples include high-profile WordPress sites being temporarily taken offline due to traffic surges generated by pingback abuse. These attacks demonstrate the critical need to monitor XML-RPC endpoints and implement traffic filtering or firewall protections.
Exploiting outdated or misconfigured sitesLink to heading
Many XML-RPC attacks succeed because sites are outdated or misconfigured. WordPress installations running older core versions or using insecure plugins can leave endpoints vulnerable to exploitation. Outdated software may contain unpatched security flaws that attackers can chain with XML-RPC requests to gain administrative privileges or inject malicious code.
Similarly, improper server configurations - such as weak file permissions or unrestricted access to API endpoints - can amplify the impact of an XML-RPC attack, turning a moderate vulnerability into a site-wide compromise. Maintaining updated software and secure configurations is therefore essential to minimize exposure to these risks.
Signs your website is being targeted by XML-RPC attacksLink to heading
Sudden spikes in server load or CPU usageLink to heading
One of the first indicators that your WordPress site may be under an XML-RPC attack is a sudden and unexplained increase in server resource usage. Brute-force attacks or pingback-based DDoS attempts send a high volume of requests to the XML-RPC endpoint, overwhelming your server. This can slow down your website dramatically, cause timeouts, or even temporarily take the site offline.
Unusual login failures or repeated failed login attemptsLink to heading
Attackers often use XML-RPC to bypass the normal login page and automate multiple password guesses. If you notice an unusual number of failed login attempts from a wide range of IP addresses, it may indicate a brute-force attack through the XML-RPC endpoint. This type of attack can go unnoticed if your site relies solely on standard login monitoring.
Unexpected traffic from unknown or suspicious IP addressesLink to heading
XML-RPC attacks often involve requests originating from multiple sources, sometimes forming a botnet. If analytics or server logs show a sudden influx of traffic from IPs that do not match your regular user base, this could be a sign of malicious activity targeting the XML-RPC interface.
How to Prevent XML-RPC AttacksLink to heading
Disable XML-RPC if not neededLink to heading
If your WordPress website does not rely on remote publishing, mobile apps, or other external integrations, disabling XML-RPC is a highly effective security measure. XML-RPC is often targeted because it exposes critical WordPress functions, such as login endpoints, to external access. Disabling it removes this attack vector entirely, preventing brute force and pingback-based DDoS attempts.
Step-by-step, this can be done by either using a dedicated security plugin that disables XML-RPC or by adding a snippet of code to your theme’s functions.php file to block external requests. This simple adjustment significantly reduces the attack surface while maintaining normal site functionality.
Limit access and rate-limit requestsLink to heading
Even when XML-RPC is needed, controlling who can access it and how frequently is crucial. Rate-limiting prevents repeated login attempts from automated scripts, mitigating brute force attacks. This can be achieved through plugins that monitor traffic and enforce request limits, or by configuring firewall rules at the server or application level.
By allowing only a controlled number of requests per IP address within a defined time frame, you can drastically reduce the effectiveness of automated attacks while maintaining legitimate user access.
Enable strong authenticationLink to heading
Authentication is the primary line of defense against unauthorized access. Implementing two-factor authentication (2FA) ensures that even if a password is compromised, attackers cannot log in without the second factor, such as a temporary code from a mobile app. Additionally, enforcing strong passwords - long, unique, and containing a mix of characters - minimizes the risk of brute force success.
Combined, these practices significantly strengthen login security, reducing the likelihood of compromise via XML-RPC endpoints.
Use a WordPress FirewallLink to heading
Deploying a Web Application Firewall (WAF) provides a proactive layer of security that filters malicious traffic before it reaches your WordPress installation. Advanced firewalls, such as W7SFW, use a deny-by-default strategy, only allowing verified safe requests to pass through.
This means that automated attack bots, suspicious IP addresses, and known exploit patterns are blocked at the network edge, rather than relying solely on WordPress to handle threats. By combining rate-limiting, traffic analysis, and customizable rulesets, a WAF ensures that both the core and plugins remain protected, even against zero-day vulnerabilities.
ConclusionLink to heading
Protecting your WordPress site from an XML-RPC attack requires both awareness and action. While XML-RPC is a convenient feature for remote communication, it can also be exploited for brute force or DDoS attacks if left unsecured. By fully implementing the security measures mentioned above, you can safeguard your website, preserve user trust, and prevent potential compromises from these sophisticated attacks.