Monday, 12 December 2016

Wordfence Blocks Username Harvesting via the New REST API in WP 4.7

WordPress 4.7 was released 6 days ago, on December 6th. It includes a REST API that will be used by many WordPress plugins, mobile apps, desktop applications, cloud services and even WordPress core in future. Every site that upgrades to WordPress 4.7 has this API enabled by default.

The API is powerful and allows WordPress to move from being a simple web based content-management system into being an application framework. What this means is that developers can write applications that run anywhere and talk to your WordPress website. So in future you’ll be able to publish content and manage your site from the cloud, from your phone, tablet or desktop and plugin developers will be able to create new kinds of extensions that improve your WordPress experience. All of these applications will use the new WordPress REST API that was released in WordPress core version 4.7.
As the saying goes, with great power comes great responsibility. Parts of this new API are available to anyone on the internet. They don’t need to sign into your WordPress website to use the API. They can just connect and use it. With the launch of this API, we expect developers to embrace it, but we also expect hackers to find ways to exploit it.
The new WordPress REST API allows anonymous access. One of the functions that it provides is that anyone can list the users on a WordPress website without registering or having an account.
This can be exploited by bots that are launching brute-force password guessing attacks on WordPress websites. They can use this API to list the usernames of anyone who has published a post on a WordPress site. The list of users displayed via this API almost always includes a user with admin level access.
To see this WP REST API function in action, simply visit a site with WordPress 4.7 installed and hit the URL:
This will list all users that have published a post. It includes that user’s userid, username, gravatar hash and website URL. We are seeing well known brand name websites that have now upgraded to WordPress 4.7, where we are able to enumerate all usernames who have published posts, simply by visiting the above URL.

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