quick-featured-images-extend.php

/*
  /wp-content/plugins/quick-featured-images/admin/class-quick-featured-images-tools.php after line 609
*/

$fimg_post_types = get_post_types( array(
    '_builtin' => false
) ); //get post types

foreach ( $fimg_post_types as $fi_cpt ) {
    if( post_type_exists( $fi_cpt ) ) {
      $this->valid_post_types[$fi_cpt] = $fi_cpt;
    }
}