Error: Permission denied to access property 'handler'

Question

I have a greasemonkey script for Firefox, which yesterday was working perfectly. I tried using it today (no code was modified) and I noticed that it stopped working. Upon fu

Answer 1

You're using unsafeWindow – that, as the name suggested, is not necessary "safe" to use – the problem probably relies there; a change was made in Firefox about objects across compartments:

https://blog.mozilla.org/addons/2014/04/10/changes-to-unsafewindow-for-the-add-on-sdk/

The blog post mention Add-on SDK, but the changes is in the platform, so it will affect Greasemonkey too.

So you basically try to get an object from one compartment (jQuery, from "unsafeWindow") and use in your greasemonkey sandbox. The way you're doing now probably can't work anymore. You can try to use the API mentioned in the article, but I'm afraid that a whole library like jQuery could have some issue to be cloned. In fact, the best way is probably load jQuery also in your Greasemonkey compartment instead of reuse the one from the page's one.

The error probably started "magically" 'cause you have updated your version of Firefox – or it gets the autoupdated.

Answer 2

This page explains how to load jQuery in a Greasemonkey script: http://wiki.greasespot.net/Third-Party_Libraries

The relevant parts are:

// @require       http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js
...
this.$ = this.jQuery = jQuery.noConflict(true);

According to the docs, jQuery.noConflict() will make sure the version of jQuery for your script won't interfere with the page.

See also: jQuery in Greasemonkey 1.0 conflicts with websites using jQuery

Answer 3

Greasemonkey 2.0 has just been pushed to all Firefox browsers set to auto-update. (GM 2 was released on June 17, 2014, but it can take a few weeks to get through the review process.)

Greasemonkey 2.0 radically changed unsafeWindow handling:

Backwards incompatible changes:

• For stability, reliability, and security the privileged sandbox has been updated to match the new changes to unsafeWindow for the Add-on SDK. In order to write values to unsafeWindow you will need to use the new methods cloneInto(), exportFunction(), and/or createObjectIn().
• The @grant none mode is now the default, and grants will no longer be implied when not explicitly provided. See the post Sandbox API Changes in Greasemonkey 2.0 for more detail.

Ordinarily, to spot-access a page function or variable, you could switch to the new methods but, in your case you are using var $ = unsafeWindow.jQuery; -- which was always a bad practice.

jQuery is a special case and cloning it back and forth is going to break things.
@require jQuery instead, EG:

// ==UserScript==
// @name        _YOUR_SCRIPT_NAME
// @include     http://YOUR_SERVER.COM/YOUR_PATH/*
// @require     http://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js
// @grant       GM_getResourceText
// @grant       GM_addStyle
// @grant       GM_xmlhttpRequest
// @grant       GM_getResourceURL
// ==/UserScript==
...