The Tor Browser / file revision

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 /* See https://bugzilla.mozilla.org/show_bug.cgi?id=813901 */

 const Cu = Components.utils;

 // Make sure that we can't inject __exposedProps__ via the proto of a COW-ed object.

 function checkThrows(expression, sb, regexp) {

   var result = Cu.evalInSandbox('(function() { try { ' + expression + '; return "allowed"; } catch (e) { return e.toString(); }})();', sb);

   dump('result: ' + result + '\n\n\n');

   do_check_true(!!regexp.exec(result));

 }

 function run_test() {

   var sb = new Cu.Sandbox('http://www.example.org');

   sb.obj = {foo: 2};

   checkThrows('obj.foo = 3;', sb, /denied/);

   Cu.evalInSandbox("var p = {__exposedProps__: {foo: 'rw'}};", sb);

   sb.obj.__proto__ = sb.p;

   checkThrows('obj.foo = 4;', sb, /__exposedProps__/);

 }