Add the itemprop, itemscope and itemtype attributes, and the meta tag to the list of allowed tags / attributes

gce-alter-allowed-tags.php

<?php
/*
Plugin name: Add microdata stuff to list of allowed tags
*/

function gce_alter_allowed_tags() {
	global $allowedposttags;

	$microdata_atts = array( 'itemprop' => true, 'itemscope' => true, 'itemtype' => true );

	$allowedposttags['div'] += $microdata_atts;
	$allowedposttags['a'] += $microdata_atts;
	$allowedposttags['img'] += $microdata_atts;
	$allowedposttags['span'] += array( 'content' => true) + $microdata_atts;
	$allowedposttags['meta'] = array( 'content' => true ) + $microdata_atts;
	$allowedposttags['time'] = array( 'datetime' => true ) + $microdata_atts;
}

add_action( 'plugins_loaded', 'gce_alter_allowed_tags' );

This is really useful because most people are worried about microdata being striped from the HTML editor / TinyMCE. The reality is that as more and more of us will be using the REST requests to communicate with wordpress, we'll still stumble on the problem.

Note that this works even if your html data is coming via WP REST API.

THANKS SO MUCH !!!