//▼画像貼り付け時の自動挿入タグを削除▼
add_filter( 'image_send_to_editor', 'remove_image_attribute', 10 );
add_filter( 'post_thumbnail_html', 'remove_image_attribute', 10 );
function remove_image_attribute( $html ){
	$html = preg_replace( '/(width|height)="\d*"\s/', '', $html );
	$html = preg_replace( '/class=[\'"]([^\'"]+)[\'"]/i', '', $html );
	return $html;
}
//▲画像貼り付け時の自動挿入タグを削除▲

function image_class_filter($class)
{
  $class = 'ariariari';
  return $class;
}
add_filter('get_image_tag_class', 'image_class_filter');