Friday, December 30, 2005

Troubleshooting 0.6.4

I thought it'd be useful to pull together all the issues you might run into with Greasemonkey itself.

We are, of course, trying to make Greasemonkey suck less, but this should help for now. Please be sure to read the error message closely so you can follow the appropriate actions for a workaround. Lots of Firefox errors look pretty similar.

Also, be sure to close Firefox and back up your profile before changing any files in your profile directory. Don't say we didn't warn you. ;)

  • If you see an error including text like this: "(NS_ERROR_FILE_NOT_FOUND) location JS frame :: chrome://greasemonkey/content/utils.js :: getContents ", follow the, uh, following steps. Updated to clarify command-line stuff: These are commands which need to be entered either in a DOS prompt or a terminal. On Windows, you can generally access this with "Start > Run > Cmd" or "Start > Run > command" or "Windows + R > command". (If someone can verify the steps for WinXP, it'd help; I don't have that OS.) On OS X, you can get there with Terminal (Applications > Terminal). On Linux, you should know how to find a terminal. ;) Once at a command prompt (C:\ in Windows, ~/user in OS X), enter the following commands, which just creates a gm_scripts directory and an empty file named config.xml in the appropriate place in your Firefox profile.

    1. cd your profile directory
    2. mkdir gm_scripts
    3. On OS X: touch gm_scripts/config.xml
    4. On Windows: echo "" > gm_scripts\config.xml

  • If you see an error including text like this: "(NS_ERROR_FAILURE) []", you're probably installing from a data: URL. If so, follow these steps:

    1. Open the link in your browser.
    2. Save the file locally, naming it [something].user.js.
    3. Open the local file in your browser.
    4. Install from the local file.

  • If you see an error as a result of a Greasemonkey action (such as installing a script) which lists a chrome URL that starts with something other than chrome://greasemonkey (such as chrome://w3rted/content/browser.xul), you probably have a naming conflict. Follow these steps:

    1. Open your profile directory\extensions\Extensions.rdf.
    2. Find the extension is in conflict by searching for the first part of the chrome URL in your error message. In the example above, I'd search for "chrome://w3rted".
    3. Find the name of that extension by looking for the value of <em:name> in the same RDF:Description.
    4. Try moving the conflicting extension below Greasemonkey by using [Tools > Extensions, right-click, Move Down]. Doing this affects the order in which extensions are loaded and sometimes allows Greasemonkey to initialize successfully. Restart Firefox before testing again.
    5. If moving the extension down didn't resolve the issue, and you can live without the other extension, disabling it should work. [Tools > Extensions, right-click, Disable]. ... And restart Firefox again.

If you're getting one of these errors and these steps didn't resolve, let me know in the comments. If you're getting a different error, I need to add it to the list. I hope this helps get you monkeying again.

Sunday, December 04, 2005

Workarounds for missing XMLHttpRequest, DOMParser, and XMLSerializer

Update: Over on the Greasemonkey mailing list, Joe la Poutre notices an even easier workaround. All you have to do is use the older form of the XPCNativeWrapper constructor to access a specific property. I'm not even sure why this works, but it does:

var parser = new XPCNativeWrapper(window, "DOMParser").DOMParser();
alert(parser.parseFromString("", "text/xml"));

Leaving the below, just for posterity...

One bittersweet part about releasing Greasemonkey 0.6.4 was that I needed to remove support for the XML Extras module which contains such goodies as XMLHttpRequest, DOMParser, and XMLSerializer.

I knew that many people were using XMLHttpRequest, particularly since GM_xmlhttpRequest, it's cross-domain replacement evaporated temporarily in 0.3.5, and that this would be a pain point. However, when weighing those people having to change their scripts to use GM_xmlhttpRequest and the alternative of having a confusingly inconsistent security model, I chose the former. I also fixed the major scripts I knew of, such as GMail Conversation Preview, which used XMLHttpRequest.

What I didn't expect at all was that people would miss DOMParser and XMLSerializer. I had no idea any scripts even used these. It's really neat to find people using pieces of your tool which you didn't expect them to, in ways you didn't expect them to. This makes me incredibly happy. Go user scripters! :-)

Anyway, to make a long story short, I've received many questions asking how to work around the lack of these two classes. The good news is that not only is there a workaround, there are three of them!

1. Use unsafeWindow.DOMParser and unsafeWindow.XMLSerializer

The downside here is that, as the name says, unsafeWindow is a reference to the content actual window - the same one that the content's JavaScript uses. Because of that, calling into it can make your script vulnerable to interference by the content script. This can be OK if you trust the site you are scripting somewhat. Take a look at the unsafeWindow details to decide whether you think this is appropriate for your script.

2. Use E4X

In a very zen turn of events it turns out that although Firefox 1.5 denies user scripters the XPCOM-based XML parsing and serializing they were accustomed to, it provides them with a brand-new - arguably superior - interface.

E4X is a brand new native JavaScript XML API that ships with Firefox 1.5 and is available to Greasemonkey scripts. There's not a ton of documentation yet, but from my experience with it so far, it's vastly more elegant and pleasant to work with than the DOM interfaces.

You can get more information about E4X, including the ECMA specification and a handy expression tester, at these URLs:

One caveat to keep in mind is that, in accordance with the E4X spec (don't ask me, it's insane), the input XML must not have an XML declaration. So you usually need to use a regex to strip it before parsing. For example:

var xml = new XML(xmlStringWithDecl.replace(/<\?xml.*?\?>/g, ""));

3. Use an IFRAME and let Mozilla do the dirty work

Many have pointed out that Mozilla already ships with an excellent, and very robust XML parser. It also ships with an HTML parser. Why not just leverage those? You can, it just takes a bit of hacking. I put an example of how to use an IFRAME to parse an HTML document into a DOM on my website.

Greasemonkey HTML Parser

Of course, just by changing the content type from text/html to text/xml, you could use the same technique to parse XHTML or even raw XML.

So I hope this shows that although the way to do certain things has changed, no capabilities have been removed from Greasemonkey. In fact new ones have been added, and the addition of completely isolating user scripts from content improved the reliability and security of Greasemonkey quite a lot.

Sorry for the disturbance, you may now resume your madcap exploration and use of Greasemonkey for all manner of things I never expected.

Mozdev back - Greasemonkey page updated

After some downtime due to increased load from the Firefox 1.5 release, mozdev is back. I took the opportunity to update the Greasemonkey homepage and authoring page.

Friday, December 02, 2005

Slides from Nov 8 Emerging Technology SIG

Last month I was asked to give a presentation about Greasemonkey at the Emerging Technology SIG here in Mountain View. I was bored with my old presentation format, so I redesigned it.

View the slides.

And here's the zipped package if you want to use the format for your own presentation.

The old format also had some issues. I found that personally, the more words that were on each slide, the more I was obligated to say on each slide. It made me uncomfortable, knowing that people would see if I didn't say something I had planned to.

My girlfriend, Susan, mentioned that I actually speak about Greasemonkey quite well off the cuff. So I stole an idea from other presentations I've seen and put very few words on each slide. I felt like this gave me more freedom to just talk - expanding on areas people seemed interested in, and skipping areas they didn't.

There is only a very vague structure to this presentation. It's divided into several high-level sections, and each section progresses through a few phases:
  • Question
  • Exploration, broad answers, more questions
  • Restate Question
  • Concise answer
I don't know if this is applicable to other presentations, but it seemed to work for Greasemonkey. Maybe Greasemonkey just has a lot of questions surrounding it :-).

Thursday, December 01, 2005

Broken Scripts Fixed

In abscense of the wiki-like features that Jesse is building into, I am keeping a list of scripts I have fixed for 0.6.4 at I'll also post a comment on the page for the scripts when I make these changes.

I'll keep the script there until the author updates the original location and pings me. If you're having trouble with a script, send a mail to the mailing list, or leave a comment, and maybe I'll take a look.

Wednesday, November 30, 2005

Greasemonkey 0.6.4

It's been a long road, but a stable, secure, and much improved Greasemonkey is now available for Firefox 1.5.

Install Greasemonkey 0.6.4

This is for Firefox 1.5 only and will not install on previous Firefoxen. If you use a Firefox version prior to 1.5, you should continue using Greasemonkey 0.5.3.

Some of the changes required for security caused minor API changes. If you are a developer and your script breaks in Greasemonkey 0.6.4, consult the wiki for information on how to fix it. Or, as always, ask on the mailing list.

What's new since 0.5.x?

  • Monkey menu: Right-click on the monkey to get quick access to enable or disable the scripts which apply to this page.

  • New install UI: There's a cute new yellow install bar like the one that's displayed for extensions when you load a user script file. When you install, you get a simple animation in the status bar for the loading progress followed by a single dialog when installation is successful.

  • New injection system: We now use a much stabler injection system which is only available to Firefox 1.5. This should solve all double-injects or non-injects.

  • The document.domain bug which was causing scripts to not inject on sites such as fixed.

  • New migration system: Greasemonkey no longer tries to migrate the script folder's location on install, which was causing install headaches for some users. Instead, it uses the old location if a previous version was already installed.

  • Fastback support: Previous Greasemonkeys interfered with Firefox 1.5's awesome Fastback feature. This release does not.

  • Remove script prefs when uninstalling the scripts. Sort of; see issues.

Known Issues:
  • When uninstalling scripts, the "also uninstall script preferences" checkbox looks works when "OK" is clicked, rather than when "uninstall" is clicked. In other words, before confirming uninstallation of scripts, make sure the checkbox is selected to also remove the associated prefs. This is needlessly confusing.

Monday, September 12, 2005

Firefox 1.5-compatible Greasemonkey beta now available

I've posted a beta of the next version of Greasemonkey to You can access it at:

This is for Firefox Beta 1.5 only and will not install on other Firefoxes. If you use a version of the browser prior to 1.5, then you should continue using Greasemonkey 0.5.3.

It's a beta, which means that it will likely break some number of your existing, working scripts. Please report these on the mailing list and to the script author. Many breakages will be up to the script author to correct. Typically, the changes required are minor. Authors should consult the Greasemonkey Wiki or mailing list for help.

There is currently no Greasemonkey 0.5.x for Firefox 1.5 beta. It's my hope that user script authors will update their scripts so that such a release is not necessary. So please, bug script authors whose scripts break :-).

What's new?
  • Monkey menu: Click the monkey to get quick access to enabling and disabling each of your scripts. You can also see at a glance which scripts ran on the current page.

  • New install UI: We no longer pop up two modal dialogs everytime you install a script. Instead, a simple animated status message to the left of the monkey tells you everything went OK.

  • New injection system: We now use a much stabler injection system which is only available to Firefox 1.5. This should solve all double-injects or non-injects (except for document.domain issues discussed below).

  • New migration system: Greasemonkey no longer tries to migrate the script folder's location on install, which was causing install headaches for some users. Instead, it uses the old location if a previous version was already installed.

  • Fastback support: Previous Greasemonkeys interfered with Firefox 1.5's awesome Fastback feature. This release does not.

Known Issues:

  • Update: If you install Greasemonkey 0.6.2 without any prior version installed, installing scripts will not work. You'll see a "file not found error. We'll be updating soon to fix this and are sorry for the bug. Meanwhile, the following will fix you up:

    1. cd <your profile directory>

    2. mkdir gm_scripts

    3. Unix: touch gm_scripts/config.xml

    4. Windows: echo "" > gm_scripts\config.xml

  • Greasemonkey 0.6.2 does not inject on websites which use the document.domain javascript property. Notable examples are and This is due to a Firefox bug which will be fixed before 1.5 ships.

  • Scripts which use any of the properties of the location object fail with NS_ERROR_INVALID_POINTER. This is due to a Firefox bug which will be fixed before 1.5 ships. As a temporary workaround, script authors may wrap code which accesses the location object with a window.setTimeout call. So for instance, instead of window.location.replace('foo'), use window.setTimeout(function(){ window.location.replace('foo') });.

XPCNativeWrapper reminders:

The window and document properties in Greasemonkey 0.6.x are XPCNativeWrapper objects, which have many annoying limitations as compared to the normal DOM objects. You can keep up with all the details as documented on the Greasemonkey wiki.

Sunday, September 04, 2005

General update

This bug with migration which everyone keeps encountering is really frustrating. It occurs on a large percentage of machines, but not for any of the Greasemonkey developers. For anyone who is still seeing problems where GM appears to not work at all after upgrading to 0.5.x, please see the directions here for a simple fix.

I have created a patch which forgoes automatic migration completely and just warns the user that they need to move the folder by hand, but I'm not sure whether to push it yet. I suppose it depends on how many people who were using 0.3.x have not yet upgraded.

In other news, I've made quite a bit of progress on a new Greasemonkey - 0.6 - which uses a more stable injection technique which should solve a whole other class of problems. It works really well, is super simple, and uses standard APIs. So I don't expect it to have the same inconsistency across machines that the 0.5 series does.

Unless I keep getting a ton of reports about bad migrations, I think I'll just leave 0.5.3 as the last of that branch and focus on 0.6, which will not have auto-migration, and thus cannot have this nasty migration bug.

I guarantee that nobody is more frustrated by these bugs than me. But 0.6 should be a lot better. So just hang on, and we can all forget 0.5 as soon as possible :-).

Saturday, September 03, 2005

0.5.3 available

Though still in the review queue on mozilla update, 0.5.3 is available for download directly from right now.

This update solves the problems with migration from 0.3.5 that some people where having with 0.5.1. It also fixes the bug that pissed a lot of people off.

I'm still working on
improving the injection system, which will solve all the random injection problems people are having. This will show up in Greasemonkey 0.6.

0.5.2 late

Somebody discovered a new injection issue (:: sigh ::) in 0.5.2, so I put it off slightly. I'll be rolling back that commit and then reposting it hopefully tonight.

These issues are highly personal, and seem to have to do with network connection, cpu speed, etc. Which is why I'm moving Greasemonkey back to a simpler injection system which should be more fool-proof.

Many people are using 0.5.x without trouble (everyone who tested the alphas on the mailing list, for example). For those of you for whom it isn't, I'm not ignoring you. The next version of Greasemonkey should work much better.

Thursday, September 01, 2005

0.3.5 -> 0.5.1 migration madness

There is a bug in the migration code for Greasemonkey 0.5.1 which is affecting some windows users. 0.5.2 fixes this issue, and has been circulated through the mailing list and is looking good, but I won't be able to post it until tonight.

If you want to fix your 0.5.1, I don't think it's a good idea to edit the profile files directly unless you really know what you're doing. Instead, these steps should fix most people's corruption.
  • Shut down Firefox.
  • Find your profile directory
  • Move profileDir/extensions/{e4a8a97b-f2ed-450b-b12d-ee082ba24781}/chrome/
    greasemonkey/content/scripts/ to profileDir/scripts.
  • Remove profileDir/gm_scripts if it exists
  • Rename profileDir/scripts to profileDir/gm_scripts
  • Restart Firefox

Thursday, August 25, 2005

Greasemonkey 0.5.1 Final


Greasemonkey 0.5.1 Final is available for download.

Special thanks to "t" for reporting a user script escalation issue in the previous beta which has now been fixed.

Other changes:
  • Bug 10107 - Allow users to select a script editor. This also allows script editing to work for *nix users.
  • Bug 11214 - Clicking "Edit" in Manager loses enable/disable changes
  • Bug 11224 - Grease monkey doesn't accept non english characters!
  • Bug 11236 - The install context menu won't show if there's a node under the A element

Sunday, August 21, 2005

Gmail Preview

Mihai rocking with another great Greasemonkey script for Gmail. This one adds full preview to your inbox items. Very smooth, a definite install.

Saturday, August 06, 2005

Aaron's OSCON 2005 slides

Some people who were at OSCON and saw my presentation asked if they would be able to get the slides online.

I've posted them to my website
. You can also download them.

OSCON was a lot of fun. Here's what I've been able to learn about Portland:
  • People: very friendly
  • summer weather: great
  • public transport: efficient and clean
  • food: superb
  • Montage: recommended
  • Burnside skaters: insane
  • Nightlife: very amusing
  • Books: available
So in general, utopia. A fine place for a nerd conference.

Tuesday, August 02, 2005

Mozdev down

It would appear that - which generously hosts Greasemonkey's website - is down today.

Luckily, the Greasemonkey installer is not actually hosted on mozdev. So you can still install Greasemonkey by going directly there.

Saturday, July 30, 2005

Greasemonkey 0.5 Beta

All of us here in Greasemonkeyland are extremely happy to announce that Greasemonkey 0.5 beta is now available for download. Horray!

It should go without saying, but: this is beta software. There will definitely be bugs. Install at your own risk.


The major news with this release is, of course, security. Greasemonkey 0.5 is much more secure than 0.3.5. Several important classes of attacks have been completely disabled and others have been made more difficult, particularly in Deer Park.
  • In Greasemonkey 0.3.4, it was possible for JavaScript on webpages you visited ("content") to use DOM mutation events, watchpoints, or Mozilla's proprietary __defineSetter__ method to get references to the special GM API functions. This has been fixed by moving user script execution away from content completely. Now, user scripts are executed in a separate object -- a "sandbox" -- which is not part of the content window. That means that content scripts cannot acccess it, and thus, cannot employ any of the tricks above to get access to the special GM APIs.

  • In earlier versions, it was possible to block Greasemonkey itself by redefining certain content DOM methods that it used to inject scripts. This has been fixed in 0.5 by only ever accessing content via the special XPCNativeWrapper objects provided by Firefox for this purpose.

  • It has long been understood and accepted that it would be possible to block individual user scripts by looking at which core DOM methods they try to use and redefining those. This will be a lot more difficult to do in Greasemonkey 0.5 when it is running on Deer Park. On Deer Park, the window and document global variables for Greasemonkey user scripts are also XPCNativeWrappers.
  • It was recently discovered that GM_xmlhttpRequest was able to access the file:// protocol and read local files. This has been fixed.

  • In all previous versions of Greasemonkey, it was trivial for content to monitor what user scripts you ran and get the source code for them. Running Deer Park and Greasemonkey 0.5, it's significantly less likely. It's still not impossible, however, so please continue to not put passwords in Greasemonkey user scripts.
Of course, no software is ever perfectly secure. Greasemonkey's entire point of existence is to mash code from two different trust domains into the same space, so it has been particularly tricky. This will be an ongoing fight. But for now, I believe that there are no known major security issues with Greasemonkey 0.5 and that it is safe to use. I also think that any future fixes will be much easier to make.


Since Greasemonkey 0.5 is actually the combination of a massive security audit and all the new code which was planned for 0.4, there are lots of new features too:
  • GM_registerMenuCommand (documentation forthcoming) now takes extra parameters to add keyboard shortcuts.

  • GM_registerMenuCommand no longer gets confused sometimes when switching tabs.

  • Greasemonkey's previous memory leakage problems have been addressed.

  • A new API, GM_openInTab has been added. You can now use a Greasemonkey user script to open a URL in a new Firefox tab.

  • A new menu item has been added: New User Script, which you can use to start a new script. It adds all the boilerplate text to the file so you can get started typing right away.

For User Script Authors

For the most part, Greasemonkey 0.5 should be perfectly backward compatible with your existing user scripts in Firefox 1.0.x. In some cases, however, it can bite you when it didn't before. Generally speaking:
  • Never add properties or functions to window. It's not safe because content can redefine these functions to mean something other than what you wrote.

    For example, you should never write code like this:
    window.handleClick = function() {
    alert("something was clicked!");
    button.setAttribute("click", "window.handleClick()");

    Instead, do it this way:
    function handleClick() {
    alert("something was clicked!");
    button.addEventListener("click", handleClick, false);

  • When you want to manipulate the DOM, always fully-qualify your expressions with window or document. So if you want to call alert on the current window, say window.alert instead of just alert. By doing this, you are sure to get the real alert method instead of a new one that content has used to overwrite the real one.

    In a future version of Greasemonkey, the ability to call methods and properties of window without this qualification will probably go away, so best to get in the habit now.

  • Keep up with the current Deer Park best practices on the Greasemonkey wiki.

  • Test in Deer Park if possible. Everything that works in Deer Park will definitely work in FF 1.0.x, but the reverse is not true. So it's best to test or develop your scripts in Deer Park for maximum compatibility.

So that's it. If you have any other questions, the Greasemonkey mailing list is, as always, the place to ask them.

Happy scripting!

Wednesday, July 27, 2005

Funny Greasemonkey quotes #17 (of a seemingly infinite series)

... [to win at the internet now], you have to make your site easily hooked into by Greasemonkey. It’s like an arms escalation race, only with hugs and easy-to-use web applications.

-- Patrick Gaskill

Greasemonkey hole proves Firefox is insecure? Not so much.

This meme has been bouncing over the net for the last few days. From Jon Udell's provocatively titled post Greasemonkey in Crisis:
"As the dust began to settle, a debate began, refracted through the lens of ideology. This time there was no Microsoft (Profile, Products, Articles) to blame. The open source underdogs had done this to themselves. And while some would argue it wasn't Firefox's fault -- since Greasemonkey is a user-installed extension -- Firefox took its share of the blame, just as Internet Explorer does when its add-ins cause trouble."
I'd just like to clarify that I don't think this proves anything about Firefox's security. Firefox - just like other browsers - has a extension system that allows users to install and run separately-developed programs within the security context of the browser, after an explicit confirmation and approval process.

The fact that such an extension has a flaw should not reflect on Firefox. The flawed code was developed separately from Firefox. It's completely different than if, for example, the browser itself had a problem which could allow an extension to be installed silently, without any user approval.

Continuing from the article:
Some say that open source software is inherently secure because the “open source process” makes it so. Wrong. Open source software, and the collaborative culture that surrounds it, have surely enhanced Firefox’s security. But also necessary is a disciplined approach to reducing the attack surface area.
I'd like to point out that Greasemonkey was the first Firefox extension I had ever written. It got very popular very quickly. The fact that it had a hole only proves that someone new to a platform can create software with holes. This shouldn't come as a surprise to anyone.

Greasemonkey 0.4.x, on the other hand, has had the benefit of much more experience on the part of it's developers. Since it is open, it has also been able to benefit from the review and advice of a community of even more senior developers. If bugs are discovered in it, they will be discussed, fixed, and scrutinizeded openly. And Greasemonkey will again be able to benefit from the advice and review of this broad community.

I think that's the main point that Open Source advocates try to make.

Tuesday, July 19, 2005

Mandatory Greasemonkey Update

Yesterday, Mark Pilgrim discovered and announced a very serious security vulnerability in Greasemonkey. The flaw allows any website which matches at least one user script (even * scripts) to read any local file on your machine, or to list the contents of local directories. The flaw applies to Greasemonkey on all platforms.

I'm working feverishly on a fix for this. But this will take several days. In the meantime, I strongly recommend that everyone either install Greasemonkey 0.3.5, or else disable or uninstall Greasemonkey completely.

Greasemonkey 0.3.5 is a "neutered" version of Greasemonkey, lacking any of the GM* APIs which make Greasemonkey scripts more powerful than regular HTML. This means that scripts which depend on GM* APIs will fail with Greasemonkey 0.3.5.

I have heard no reports of this flaw being exploited, but now that it's public knowledge it isn't safe to continue using any version of Greasemonkey other than 0.3.5. Please either upgrade to 0.3.5 or disable Greasemonkey until I can get a fix finished.

I'm aware of how badly this sucks for many of you. Please accept my deepest personal apologies and realize that I'll do my best to get a fixed Greasemonkey available just as soon as possible.

If you have any other questions, the Greasemonkey mailing list is a good place to ask them.

Monday, July 18, 2005

Please do not put private keys in user scripts (yet)

Joe Gregorio wrote a really interesting piece on about sending encrypted data over insecure networks, using Greasemonkey to decrypt it on the client.

In his demo, Joe lists his private key in the user script source.

Please do not put private information into user script source code, yet

As a side-effect of the way that we are currently injecting user scripts, it's possible for malicious sites to sniff their contents. So, for example, if Bloglines got hacked, or somebody exploited a XSS vulnerability to get Bloglines to include their JavaScript in a feed, then Joe's private key could get stolen.

We're thinking about ways to run user scripts completely separate from the DOM, which would prevent this sniffing from being possible, but it doesn't exist yet. I'll post again here when that happens.


If you are an XPCOM/Mozilla/JavaScript expert, Greasemonkey needs you. We are looking for a way to execute JavaScript programatically with these restrictions:
  1. browser content window is the global object
  2. script runs in same security context as browser content is currently running in
  3. we have the ability to add other global objects of our choosing
I've looked into mozIJSSubScriptLoader, but it does not seem to solve any of these well or 2) at all. Post in the comments or on the Greasemonkey mailing list if you have a solution.