Index: wp-admin/includes/plugin-install.php
===================================================================
--- wp-admin/includes/plugin-install.php	(revision 14368)
+++ wp-admin/includes/plugin-install.php	(working copy)
@@ -439,7 +439,7 @@
 				$update_file = $file;
 				$version = $plugin->new_version;
 				if ( current_user_can('update_plugins') )
-					$url = wp_nonce_url(admin_url('update.php?action=upgrade-plugin&plugin=' . $update_file), 'upgrade-plugin_' . $update_file);
+					$url = admin_url( wp_nonce_url( 'update.php', 'upgrade-plugin_' . $update_file) . '&action=upgrade-plugin&plugin=' . $update_file);
 				break;
 			}
 		}
@@ -450,7 +450,7 @@
 			$installed_plugin = get_plugins('/' . $api->slug);
 			if ( empty($installed_plugin) ) {
 				if ( current_user_can('install_plugins') )
-					$url = wp_nonce_url(admin_url('update.php?action=install-plugin&plugin=' . $api->slug), 'install-plugin_' . $api->slug);
+					$url = admin_url( wp_nonce_url( 'update.php', 'install-plugin_' . $api->slug ) . '&action=install-plugin&plugin=' . $api->slug );
 			} else {
 				$key = array_shift( $key = array_keys($installed_plugin) ); //Use the first plugin regardless of the name, Could have issues for multiple-plugins in one directory if they share different version numbers
 				if ( version_compare($api->version, $installed_plugin[ $key ]['Version'], '=') ){
@@ -470,7 +470,7 @@
 		} else {
 			// "install" & no directory with that slug
 			if ( current_user_can('install_plugins') )
-				$url = wp_nonce_url(admin_url('update.php?action=install-plugin&plugin=' . $api->slug), 'install-plugin_' . $api->slug);
+				$url = admin_url( wp_nonce_url( 'update.php', 'install-plugin_' . $api->slug ) . '&action=install-plugin&plugin=' . $api->slug );
 		}
 	}