Index: wp-includes/class-oembed.php
===================================================================
--- wp-includes/class-oembed.php	(revision 12411)
+++ wp-includes/class-oembed.php	(working copy)
@@ -71,7 +71,7 @@
 		$provider = false;
 
 		if ( !isset($args['discover']) )
-			$args['discover'] = true;
+			$args['discover'] = false;
 
 		foreach ( $this->providers as $matchmask => $data ) {
 			list( $providerurl, $regex ) = $data;