XML-RPC on WordPress is actually an API or “application program interface“. It gives developers who make mobile apps, desktop apps, and other services the ability to talk to your WordPress site. The XML-RPC API that WordPress provides gives developers a way to write applications (for you) that can do many of the things that you can do when logged into WordPress via the web interface.

These include:

  • Publish a post
  • Edit a post
  • Delete a post.
  • Upload a new file (e.g. an image for a post)
  • Get a list of comments
  • Edit comments

For a full list of the WordPress API functions available to developers via XML-RPC, take a look at this page on the WordPress codex.

If you disable the XML-RPC service on WordPress, you lose the ability for any application to use this API to talk to WordPress.

Let’s use an example to illustrate: You have an app on your iPhone that lets you moderate WordPress comments. Someone advises you to disable XML-RPC. Your iPhone app suddenly stops working because it can no longer communicate with your website using the API you just disabled.

There are two common attacks on XML-RPC:

  • DDoS via XML-RPC pingbacks.
  • Brute force attacks via XML-RPC.

If you still want to disable XML-RPC, you can switch on this option in Hide My WordPress 3.