Source

File: wp-admin/includes/media.php

function get_upload_iframe_src( $type = null, $post_id = null, $tab = null ) {
	global $post_ID;

	if ( empty( $post_id ) ) {
		$post_id = $post_ID;
	}

	$upload_iframe_src = add_query_arg( 'post_id', (int) $post_id, admin_url( 'media-upload.php' ) );

	if ( $type && 'media' !== $type ) {
		$upload_iframe_src = add_query_arg( 'type', $type, $upload_iframe_src );
	}

	if ( ! empty( $tab ) ) {
		$upload_iframe_src = add_query_arg( 'tab', $tab, $upload_iframe_src );
	}

	/**
	 * Filters the upload iframe source URL for a specific media type.
	 *
	 * The dynamic portion of the hook name, `$type`, refers to the type
	 * of media uploaded.
	 *
	 * @since 3.0.0
	 *
	 * @param string $upload_iframe_src The upload iframe source URL by type.
	 */
	$upload_iframe_src = apply_filters( "{$type}_upload_iframe_src", $upload_iframe_src );

	return add_query_arg( 'TB_iframe', true, $upload_iframe_src );
}