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Decouple authors from users. Instead of using users as authors use a special taxonomy for it.
The plugin gives a simple way to have “guest author”, user generated content, multiple authors, 
or any other setting in which you might not want to give people access permissions to the admin 
side of WordPress but still want to give credit to the author and have some way to aggregate 
his/hers posts on the site.
You can combine this plugin with any other plugin which prevent user enumeration to prevent 
user name leakage and
Read more on the plugins main page https://calmpress.org/authors-as-taxonomy/
<h4>Documentation</h4>
<h4>Contribute</h4>
Pull Requests, bug reports and/or enhancement suggestions are welcome at https://github.com/calmPress/Authors-as-taxonomy

Authors as Taxonomy

Decouple authors from users. Instead of using users as authors use a special taxonomy for it.

Stops user name enumeration and other type of user name and email leakages.
Specifically does the following: 
1. When the site is configured to use pretty permalinks, the plugin will prevent 
 the automatic redirect of usrl which include user ID, like example.com/?author=1, to 
 something like example.com/author/admin which will leak the existence of a user 
 named admin which can be used in further brute force attacks. 
 (This is also know as “user enumeration”).
<ol>
<li>
With the REST API restrict user name related information (actual user name 
and user posts page URL) to only admin users.
</li>
<li>
Preventing authentication failure notices on the login page to disclose 
the existence of user names/user emails resulting from displaying different 
messages hen the user is incorrect and when the password is incorrect. Just 
display the same failure message for whatever is the failure reason.
</li>
<li>
Preventing the reset password mechanism from disclosing user names/user emails 
resulting from displaying different messages when a user/email for which a reset 
is requested exist in the DB, and when it does not. Just display the same message 
for both.
</li>
</ol>
Even with the plugin active, if your theme displays author information while linking 
to author pages this can be used for user name leakage. In this case you should 
think about totally decoupling user and author information with plugins like 
https://wordpress.org/plugins/authors-as-taxonomy/
Another thing that the plugin do not do is to handle leakage resulting from the use 
of gravatar, as this requires a replacement of gravatar functionality itself and 
it is much harder to exploit than the other leakages.
And last leakage hole not covered right now, but might be covered in the future, 
is leakage of information via the sign in process. We leave it for later as most 
installs do not allow people to sign in.
Read more on the plugins main page https://calmpress.org/wordpress-plugins/prevent-user-name-and-email-leakage/
<h4>Documentation</h4>
<h4>Contribute</h4>
Pull Requests, bug reports and/or enhancement suggestions are welcome at https://github.com/calmPress/Authors-as-taxonomy

Prevent user name and email leakage

Stops user name enumeration and other type of user name and email leakages.

Authors as Taxonomy vs Prevent user name and email leakage