What is 'xmlrpc.php'?
'xmlrpc.php' is a PHP script file that implements the XML-RPC (Extensible Markup Language Remote Procedure Call) protocol in WordPress and some other PHP-based systems. XML-RPC was designed to allow for the execution of remote procedures or methods over the internet using XML as the data format for communication.
History and Context
XML-RPC was created in 1998 by Dave Winer of UserLand Software and Microsoft's Mohsen Al-Ghosein. The protocol was designed to be simple, platform-independent, and to facilitate the creation of web services by allowing applications to make remote procedure calls over HTTP. WordPress adopted XML-RPC for several reasons:
- Remote Publishing: XML-RPC enabled bloggers to publish posts from remote clients like Windows Live Writer, MarsEdit, or mobile apps.
- API Access: It provided an API for developers to interact with WordPress programmatically, allowing for content management, user authentication, and other administrative tasks.
Functionality in WordPress
In WordPress, 'xmlrpc.php' enables the following key functionalities:
- Content Management: Allows for remote creation, editing, and deletion of posts, pages, and comments.
- User Authentication: Facilitates login from external applications, allowing users to authenticate against their WordPress site.
- Pingbacks and Trackbacks: Used for sending and receiving pingbacks and trackbacks, which notify other blogs when a link has been made to their content.
- Web Services: Can be used to expose WordPress functionality as a web service, allowing other applications to interact with the site's content.
Security Concerns
The 'xmlrpc.php' file has been a target for various security vulnerabilities:
- Brute Force Attacks: The file can be exploited for brute force attacks due to its authentication capabilities.
- DDoS Attacks: The ability to make multiple requests can be leveraged for Distributed Denial of Service attacks.
- Vulnerabilities: Over time, several vulnerabilities have been discovered and patched, such as the infamous XML-RPC DDoS vulnerability.
Due to these security concerns, many WordPress administrators choose to disable XML-RPC or restrict its access.
Disabling XML-RPC
To disable XML-RPC, WordPress users can:
- Add a line to the wp-config.php file:
define('XMLRPC_REQUEST', false);
- Use a security plugin like Wordfence or iThemes Security to block or limit XML-RPC access.
Despite these issues, XML-RPC still has its uses, especially for developers who need to integrate WordPress with other systems or applications.
References