Source

File: wp-admin/includes/bookmark.php

function edit_link( $link_id = 0 ) {
	if ( ! current_user_can( 'manage_links' ) ) {
		wp_die(
			'<h1>' . __( 'You need a higher level of permission.' ) . '</h1>' .
			'<p>' . __( 'Sorry, you are not allowed to edit the links for this site.' ) . '</p>',
			403
		);
	}

	$_POST['link_url']   = esc_html( $_POST['link_url'] );
	$_POST['link_url']   = esc_url( $_POST['link_url'] );
	$_POST['link_name']  = esc_html( $_POST['link_name'] );
	$_POST['link_image'] = esc_html( $_POST['link_image'] );
	$_POST['link_rss']   = esc_url( $_POST['link_rss'] );
	if ( ! isset( $_POST['link_visible'] ) || 'N' !== $_POST['link_visible'] ) {
		$_POST['link_visible'] = 'Y';
	}

	if ( ! empty( $link_id ) ) {
		$_POST['link_id'] = $link_id;
		return wp_update_link( $_POST );
	} else {
		return wp_insert_link( $_POST );
	}
}