Upgrade/Install: Sanitize file name in File_Upload_Upgrader.

Merge of [38524] to the 3.7 branch.
Built from https://develop.svn.wordpress.org/branches/3.7@38534


git-svn-id: http://core.svn.wordpress.org/branches/3.7@38475 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/class-wp-upgrader.php

@@ -1602,8 +1602,12 @@ function __construct($form, $urlholder) {
 			if ( ! ( ( $uploads = wp_upload_dir() ) && false === $uploads['error'] ) )
 				wp_die( $uploads['error'] );
 
-			$this->filename = $_GET[$urlholder];
+			$this->filename = sanitize_file_name( $_GET[ $urlholder ] );
 			$this->package = $uploads['basedir'] . '/' . $this->filename;
+
+			if ( 0 !== strpos( realpath( $this->package ), realpath( $uploads['basedir'] ) ) ) {
+				wp_die( __( 'Please select a file' ) );
+			}
 		}
 	}