Firefox 17 Compatibility Update

Firefox 17 was released yesterday, and there a couple of notable compatibility issues that have surfaced and are worth pointing out.

Tab Mix Plus currently incompatible

The popular Tab Mix Plus extension is causing some problems for users in Firefox 17. The problems include broken menu items – like the one that opens the Add-ons Manager – and broken links in Firefox windows, like the About dialog.

This extension broke due to bug 761723, and a fixed version hasn’t been released to AMO yet. Apparently there’s a development version of Tab Mix Plus that fixes these issues, so hopefully it will be pushed to the general public soon.

In the meantime, we recommend users to disable the add-on until the new update is released.

toString() compatibility warning

We ran the automatic compatibility upgrade last week, emailing developers who have add-ons on AMO about their compatibility status. This included a warning for using eval and the Function constructor, since these are often used to monkeypatch Firefox functions, and they most likely broke due to bug 761723.

This is the message that you should see if your add-on was flagged:

The `toString` implementation for function objects have changed. If you are using `eval` or `Function` to change the behavior of ‘native’ functions, it is probably not working correctly in Firefox 17 and above.

Unfortunately, this warning is appearing on many more add-ons that we intended. Notably, it will show up for all add-ons using the jquery library, or any other libraries that use eval of the Function constructor.

In these cases, you don’t need to worry about the warnings. They’re false positives and can be easily ignored. Also, even if you got a message from us indicating your add-on didn’t pass our compatibility checks, you don’t need to take any action for your add-on to remain compatible with Firefox 17 and above. Because of the Default to Compatible feature, all add-ons remain compatible, even if they don’t pass our checks. However, we always recommend that you test your add-on with every new release and make sure everything still works.

Binary compatibility briefly broken before release

We assure developers of binary add-ons that they can build their binaries based off of the first beta for every Firefox version. This gives them 6 weeks to have their add-ons ready before a new version is released to the public.

Unfortunately, we overlooked a change that broke binary compatibility in Firefox 17 beta 6. This was reported as bug 813264 and quickly fixed on Firefox 17 beta 7, which made it to release.

So, if you built your binary add-on based on the early Firefox 17 betas, you don’t need to do anything. If you built your binaries based on beta 6, you’ll need to rebuild them using beta 7 or the release version. We apologize for the inconvenience, and will look into ways to ensure this doesn’t happen again.

42 comments on “Firefox 17 Compatibility Update”

  1. LouCypher wrote on

    Tab Mix Plus users can install the latest dev build ( at to solve the compatibility issue.

    1. Otite wrote on

      Tab Mix Plus 0.4.4pre.120724b = very good !

  2. Tonmoy wrote on

    I can not install Firefox 17 . It is always saying file is corrupt. I am using Windows 7 . Please help.

    1. Jorge Villalobos wrote on

      I recommend you visit our support site for help with this.

      1. Gary wrote on

        Unless you use a 64-bit version of windows, then you are on your own.

  3. Janesh wrote on

    FCKEditer doesn’t work, any clue regarding this?

    1. Jorge Villalobos wrote on

      What doesn’t work? Have you tried contacting the developer?

      1. Samir wrote on,
        this sol doesn’t work for FCKEditor.
        wat is the solution.

  4. Offsprung wrote on

    Usually FFx updates only break plugins, this time…all bookmarks do nothing, reload does nothing, forward and back nav even from dropdown do nothing! Go to support and help moz troubleshoot a release that never should have happened? I will attempt to find 16 and try to downgrade and ignore the prompts of new releases since they are not properly vetted before release. I should know better, same people that left us in the lurch with nutscrape….

    1. Offsprung wrote on

      16 downloads pulled due to release with a huge security hole? So 15? LMAO!!!

      1. Offsprung wrote on

        Simple “upgrade” to 16.0.2 and nearly ALL bugs vanish. Except app tab but who cares about app tabs which were probably buggy the whole time. 😉

        1. Jorge Villalobos wrote on

          Are you using Tab Mix Plus, by chance?

          1. Offsprung wrote on


    2. Yuhong Bao wrote on

      I never had that problem. Are you assuming everyone had that problem?

    3. Darrell MacLennan wrote on

      Same problem….I used Mozbackup to restore my bookmarks without anything else, same problem – clean install.

  5. Alain ANDRE wrote on

    Hi guys, I have created an add-on wish allows people of my company to launch .exe, mailing lists, point to system dir etc from FF. Everything worked perfectly until FF17. I have this error comming:
    TypeError: is undefined.

    Here’s a function example inside the object :
    var file = Components.classes[“;1”].
    file.initWithPath(path); file.launch();
    } catch(e) { this.Log(e); }

    I cannot find any developer’s infos about this issue. Can I get some link or help please.

    1. Jorge Villalobos wrote on

      enablePrivilege has been deprecated for a very long time. See this bug for some discussion about it.

      If this is add-on code, then you don’t need to use enablePrivilege at all, you can just remove it and the code will continue to work.

      1. Alain ANDRE wrote on

        Thanks, it works perfectly without it … and thank you for the link to the bug.

  6. Stephen Corlett wrote on

    I am regretting upgrading to Firefox 17 as my passwords no longer auto fill either from Firefox-saved or from Norton safe. Frustrating.

  7. wibie wrote on

    I CAN’T press ENTER in ‘Go to a website’ bar. This happened after installing FF17. This ever happened before in previous version.

  8. TMPlover wrote on

    please just check/verify the dev version and include it in AMO… This is one of THE addons which make FF what it is. 🙁

    1. Jorge Villalobos wrote on

      Submitting the new version to AMO is up to the developer. We’re waiting for it as anxiously as you are.

  9. Christian wrote on

    My scripts from Sothink DHMTL Menu V7 does not work anymore with FF17.
    Everyting was OK with 16.

  10. rv wrote on

    I had quite some info on Tab Mix Plus (studies research)
    when will it be available?
    Will it be possible to restore sessions saved in .JSON files?
    Anyother application doing same as Tab Mix Plus?

    Thank you Jorge & Happy Working Time (“,) rv

  11. Gary wrote on

    Although I currently have Firefox installed, it is not used. Pretty damn buggy and uses FAR too much memory. It is a total resource hog. Until somebody somewhere some day decides to REALLY address issues with Firefox, try Comodo Dragon ( It takes a little getting used to, but performance-wise, it leaves Firefox in the dust.

    1. Trev wrote on

      Hardly a replacement — Windows only! No good for my OSX and FreeBSD systems.

  12. Yuhong Bao wrote on

    Have checking for add-on compatibility before upgrade been considered?

  13. Cece wrote on

    Since installing the 17.0.1 update, I get this error on every page that loads: [Javascript Application] Error: Syntax Error. How do I fix this?

    1. Jorge Villalobos wrote on

      Do you mean you see it on every page, or is it something that appears in the Error Console? Do you have any add-ons installed?

  14. Fixitman wrote on

    As always, stuff broke when Mozilla released this version. I always wait at least two years before “upgrading” any software like this, and they’re on a SIX WEEK release schedule? No thanks. They’re just asking for trouble. “Oh but the developers of the addons have to make sure THEY meet OUR new buggy software” just doesn’t cut it with me. I want my OLD addons or extensions to work without having to mess with them.
    When will Mozilla get it through their heads that they shouldn’t BREAK stuff in trying to release something “new” so often. Make the new versions of FFx compatable with addons or extensions going all the way back to at least 3.6, and not have to spend 6 weeks “tweaking” a new release just to make it work the way I want, and just have them turn around and break it again.
    Chrome doesn’t have these problems, from what I’ve seen, not that I like Chrome at all. They also don’t make a big deal out of their release schedule. Truth is, Mozilla is mostly funded by Google and Google is trying its damndest to put them out of business and/or make them irrelevant. So, Classic 3.6 for me AGAIN.

    1. Jorge Villalobos wrote on

      You might be interested in the ESR flavor. It’s not meant for individuals, but you can get it and use it if you want.

  15. Reg frae Tweedbank wrote on

    Why suddenly, after Firefox download upgrade, does Norton NIS not detect any cookies? If I use IE9 to visit sites and then run an NIS scan cookies are found but they are not found if I use Mozilla Firefox?
    Puzzled I am (says Yoda)

  16. Diane OG wrote on

    Ever since the latest update, when I hit ‘file’ and try to ‘add tab’ it does not work. I have to open another window. I am not a techie, but familiar with IT to some extent. Is the the problem you have been talking about regarding the add-on :tab mix plus’? Please help. thanks.

    1. Jorge Villalobos wrote on

      Are you using Tab Mix Plus? The Add Tab option isn’t part of Firefox, so it is likely that it was added by this add-on and it is still broken.

  17. Neil thomson wrote on

    I have always used mozilla , but very 17 is poor .
    there a re anumber of issues
    1. It hangs when inputting signon to a website / account , then it locks up as @program is not responding’. When it is closed it seem to hang onto the browser internet access so no other browers will run ( eg Chrome) the only way to solve the problem is to switch off and start again. It is incredibly slow to start up.
    I have run iobit malware – no issues
    I reset firefox to all the default settings to no avail..
    I have now reverted back to version 14,0.1 and this is working perfectly.
    I really like this browser but the latest versions are just full of basic errors.
    regards Neil

    1. Jorge Villalobos wrote on

      Is there a particular website causing you these log in problems, or is it all of them? Do you have any add-ons installed that do password management, by chance?

  18. Christopher Heckman wrote on

    Ad Blocker doesn’t work any more.

  19. Tom Hartman wrote on

    After I downloaded Firefox 17 I have had a great number of various “can’t load” messages which resolves itself if I hit “Try again” enough times.
    I also get many sites such as weather .com in a stream down the left side of my screen.
    Again if I reload it enough times it comes up properly.
    Please don’t tell me I have to go back to Explorer, which is not giving me any of these problems.

  20. raghavapuram wrote on

    I have created a sidebar extension. And, i am getting ‘Components.classes’ is undefined error on firefox 17 (it is working fine on previous browsers)

    // (‘UniversalXPConnect’);
    var rk = Components.classes[“;1”].createInstance(Components.interfaces.nsIWindowsRegKey);

    Can I get some help on this issue.

    1. Jorge Villalobos wrote on

      It sounds like you’re trying to run that code in a content frame instead of a chrome frame.

      1. Asif wrote on

        I am also facing similar problem. I am not sure if I am using a content frame or a chrome frame. How do I find that out?

        Sorry for the naive question, I am new to this.

        1. Jorge Villalobos wrote on

          If Components.classes is undefined, it means you’re in a content window. This article might be useful for you.