diff -r 000000000000 -r 6474c204b198 js/xpconnect/tests/unit/test_bug813901.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/xpconnect/tests/unit/test_bug813901.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,25 @@
+/* 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__/);
+}