Carlos

In many WordPress installations is possible enumerate usernames through the author archives, using urls like this:
http://wpsite/?author=1
http://wpsite/?author=1/
http://wpsite/?bypass=1&author%00=1
http://wpsite/?author%00=%001
http://wpsite/?%61uthor=1
And recently wordpress since 4.7 comes with a rest api integrated that allow list users:
curl -s http://wpsite/wp-json/wp/v2/users/ 
curl -s http://wpsite/?rest_route=/wp/v2/users 
curl http://wpsite/?_method=GET -d rest_route=/wp/v2/users
Know the username of a administrator is the half battle, now an attacker only need guest the password. 
This plugin stop it.
Also, is possible get usernames from the post entries. 
This plugin, hide the name of the author in a post entry if he is not using a nickname. 
Also, hide the url page link of an administrator author.
The main goal is hide the administrators usernames. 
Obviously, is better not choose “admin” as the username because is easiliy guessable.

No User Enumeration

mgm security partners GmbH

WP Author Security is a lightweight but powerful plugin to protect against user enumeration attacks on author pages and other places where valid user names can be obtained.
By default, WordPress will display some sensitive information on author pages. 
The author page is typically called by requesting the URI <code>https://yourdomain.tld/?author=<id></code> or with permalinks <code>https://yourdomain.tld/author/<username></code>. 
The page will include (depending on your theme) the full name (first and last name) as well as the username of the author which is used to log in to WordPress.
In some cases, it is not wanted to expose this information to the public. An attacker is able to brute force valid IDs or valid usernames. This information might be used for further attacks like social engineering attacks or log in brute force attacks with gathered usernames. 
However, when using the plugin and you disable author pages completely it must be noted that you need to take care that your active theme will not display the author name itself on posts like “Posted by admin” or something like that. This is something the plugin will not handle (at the moment).
By using the extension, you are able to disable the author pages either completely or display them only when the author has at least one published post. When the page is disabled the default 404 error page of the active theme is displayed.
In addition, the plugin will also protect other locations which are commonly used by attackers to gather valid user names. These are:
<ul>
<li>The REST API for users which will list all users with published posts by default. 
 https://yourdomain.tld/wp-json/wp/v2/users</li>
<li>The log in page where different error messages will indicate whether an entered user name or mail address exists or not. The plugin will display a neutral error message independently whether the user exists or not.</li>
<li>The password forgotten function will also allow an attacker to check for the existence of a user. As for the log in page the plugin will display a neutral message even when the user does not exists.</li>
<li>Requesting the feed endpoint /feed of your blog will also allow others to see the username or display name of the author. The plugin will remove the name from the result list.</li>
<li>WordPress supports so-called oEmbeds. This is a technique to embed a reference to a post into another post. However, this reference will also contain the author name and a direct link to the profile page. The plugin will also remove the name and link here.</li>
<li>Since WordPress 5.5 a default sitemap can be reached via /wp-sitemap.xml. This sitemap will disclose the usernames of all authors. If this should not be disclosed you are able to disable this feature of WordPress.</li>
</ul>

WP Author Security

Protect against user enumeration attacks on author pages and other places where valid user names can be obtained.

No User Enumeration vs WP Author Security