Index: comment.php
===================================================================
--- comment.php	(revision 15277)
+++ comment.php	(working copy)
@@ -82,10 +82,12 @@
 	if ( 1 == get_option('comment_whitelist')) {
 		if ( 'trackback' == $comment_type || 'pingback' == $comment_type ) { // check if domain is in blogroll
 			$uri = parse_url($url);
+			if ( empty($uri['scheme']) )
+				$uri['scheme'] = 'http';
 			$domain = $uri['host'];
 			$uri = parse_url( home_url() );
 			$home_domain = $uri['host'];
-			if ( $wpdb->get_var($wpdb->prepare("SELECT link_id FROM $wpdb->links WHERE link_url LIKE (%s) LIMIT 1", '%'.$domain.'%')) || $domain == $home_domain )
+			if ( $wpdb->get_var($wpdb->prepare("SELECT link_id FROM $wpdb->links WHERE link_url LIKE (%s) LIMIT 1", like_escape($uri['scheme'] . '://' . $domain) . '%')) || $domain == $home_domain )
 				return true;
 			else
 				return false;