WordPress Version: 5.1
/**
* Filters the latest content for preview from the post autosave.
*
* @since 2.7.0
* @access private
*/
function _show_post_preview()
{
if (isset($_GET['preview_id']) && isset($_GET['preview_nonce'])) {
$id = (int) $_GET['preview_id'];
if (false === wp_verify_nonce($_GET['preview_nonce'], 'post_preview_' . $id)) {
wp_die(__('Sorry, you are not allowed to preview drafts.'), 403);
}
add_filter('the_preview', '_set_preview');
}
}