Index: includes/class-wp-upgrader.php
===================================================================
--- includes/class-wp-upgrader.php	(revision 12404)
+++ includes/class-wp-upgrader.php	(working copy)
@@ -504,6 +504,8 @@
 		$this->maintenance_mode(false);
 		$this->skin->footer();
 
+		echo '<p><a href="' . admin_url('update-core.php') . '">' . __('Go back') . '</a></p>';
+
 		// Cleanup our hooks, incase something else does a upgrade on this connection.
 		remove_filter('upgrader_clear_destination', array(&$this, 'delete_old_plugin'));