public static function cleanup_old_data() {
		global $wpdb;

		$popup_groups = array(
			'display',
			'close',
			'click_open',
			'auto_open',
			'admin_debug',
		);

		$popup_fields = array();

		foreach ( $popup_groups as $group ) {
			foreach ( apply_filters( 'popmake_popup_meta_field_group_' . $group, array() ) as $field ) {
				$popup_fields[] = 'popup_' . $group . '_' . $field;
			}
		}

		$popup_fields = implode( "','", $popup_fields );

		$wpdb->query( "DELETE FROM $wpdb->postmeta WHERE meta_key IN('$popup_fields');" );
	}