invisnet

The REST API is essential for any modern web framework, but with it comes a huge attack surface. WP REST API Security reduces the attack surface by disabling all the REST API endpoints by default, allowing you to enable only those actually needed. Those that are enabled require authentication by default, allowing you to choose which to make public.
<blockquote>
N.B. If you are using the new Block Editor you must keep nearly all the endpoints enabled for it to work, but none need be public.
</blockquote>

WP REST API Security

Provides a UI to control which REST API endpoints are enabled and which require authentication.

Enrico Sorcinelli

JSON REST API and XML-RPC API are powerful ways to remotely interact with WordPress.
If you don’t have external applications that need to communicate with your WordPress instance using JSON REST API or XML-RPC API you should disable access to them for external requests.
In the standard WordPress installation JSON REST API and XML-RPC API are enabled by default. 
In particular the REST API is turned on also for unlogged users. This means that your WordPress instance is potentially leaking data, for example anyone could be able to:
<ul>
<li>copy easily your published contents natively with the REST API (and not with a web crawler);</li>
<li>get the list of all users (with their ID, nickname and name);</li>
<li>retrieve other information that you didn’t want to be public (such as an unlisted published page or a saved media not yet used).</li>
</ul>
Even if you could do the stuff by writing your own code using native filters, this plugin aims to help you to control JSON REST API and XML-RPC API accesses from the administration panel or programmatically by a simple API filter.
<h3>Basic Features</h3>
<ul>
<li>Disable REST API interface for unlogged users.</li>
<li>Disable JSONP support on REST API.</li>
<li>Add Basic Authentication to REST API.</li>
<li>Remove REST <code><link></code> tags, REST <code>Link</code> HTTP header and REST Really Simple Discovery (RSD) informations.</li>
<li>Setup trusted users, IP/Networks and endpoints for unlogged users REST requests.</li>
<li>Change REST endpoint prefix.</li>
<li>Disable XML-RPC API interface.</li>
<li>Remove <code><link></code> to the Really Simple Discovery (RDS) informations.</li>
<li>Remove <code>X-Pingback</code> HTTP header.</li>
<li>Setup trusted users, IP/Networks and methods for XML-RPC requests.</li>
<li>Show user’s access informations in users list administration screen.</li>
</ul>
<h3>Usage</h3>
Once the plugin is installed you can control settings in the following ways:
<ul>
<li>Using the Settings->REST XML-RPC Data Checker administration screen.</li>
<li>Programmatically, by using <code>rest_xmlrpc_data_checker_settings</code> filter (see below).</li>
</ul>
<h3>API</h3>
<h4>Hooks</h4>
<code>rest_xmlrpc_data_checker_settings</code>
Filters plugin settings values.
<pre><code>apply_filters( 'rest_xmlrpc_data_checker_settings', array $settings )
</code></pre>
<code>rest_xmlrpc_data_checker_admin_settings</code>
Filter allowing to display or not the plugin settings page in the administration.
<pre><code>apply_filters( 'rest_xmlrpc_data_checker_admin_settings', boolean $display )
</code></pre>
<code>rest_xmlrpc_data_checker_rest_error</code>
Filter JSON REST authentication error after plugin checks.
<pre><code>apply_filters( 'rest_xmlrpc_data_checker_rest_error', WP_Error|boolean $result )
</code></pre>
<code>xmlrpc_before_insert_post</code>
Filter XML-RPC post data to be inserted via XML-RPC before to insert post into database.
<pre><code>apply_filters( 'xmlrpc_before_insert_post', array|IXR_Error $content_struct, WP_User $user )
</code></pre>

REST XML-RPC Data Checker

REST XML-RPC Data Checker allow to check JSON REST and XML-RPC API requests and grant access permissions.

WP REST API Security vs REST XML-RPC Data Checker