Index: wp-admin/includes/theme-install.php
===================================================================
--- wp-admin/includes/theme-install.php	(revision 10927)
+++ wp-admin/includes/theme-install.php	(working copy)
@@ -616,10 +616,12 @@
 		return;
 	}
 
-	$theme = isset($_REQUEST['theme']) ? stripslashes( $_REQUEST['theme'] ) : '';
+	$theme        = isset($_REQUEST['theme'])        ? stripslashes( $_REQUEST['theme'] )        : '';
+	$theme_name   = isset($_REQUEST['theme_name'])   ? stripslashes( $_REQUEST['theme_name'] )   : '';
+	$download_url = isset($_REQUEST['download_url']) ? stripslashes( $_REQUEST['download_url'] ) : '';
 
 	$url = 'theme-install.php?tab=install';
-	$url = add_query_arg(array('theme' => $theme, 'theme_name' => stripslashes( $_REQUEST['theme_name'] ), 'download_url' => stripslashes( $_REQUEST['download_url'] ) ), $url);
+	$url = add_query_arg(array('theme' => $theme, 'theme_name' => $theme_name, 'download_url' => $download_url ), $url);
 
 	$url = wp_nonce_url($url, 'install-theme_' . $theme);
 	if ( false === ($credentials = request_filesystem_credentials($url)) )