Mozilla releases Firefox 40.0.2 update to fix issues in the browser

Martin Brinkmann
Aug 14, 2015
Updated • Aug 14, 2015

Firefox 40 was released on Tuesday and the release of an update shortly afterwards is usually a good indicator that something went terribly wrong and needs fixing immediately.

The organization published release notes for Firefox 40.0.1 shortly after release of Firefox 40 to the stable channel. It pulled the release notes shortly thereafter again, and published release notes for Firefox 40.0.2 instead.

If you run Firefox Stable, you are probably wondering about those updates.

According to the release notes, they fix two issues in Firefox and add one new feature to it at the same time:

  1. A startup crash issue was fixed that happened under certain conditions. It affects only Windows systems Firefox is running on, and was first reported in April 2015. Consult Bug 1160295 for further information about the issue.
  2. The component mozalloc.lib is missing in 32-bit versions of Firefox for Windows. Again a bug that is only affecting Windows versions of Firefox, or more precisely the SDK. Consult Bug 1168291 for additional information.


The new "feature" fixes an issue on Windows 10 where a click on the "let's do it" button to set Firefox as the default browser on Windows 10 lead to a Windows message instead of opening the default settings app which users have to use to set Firefox as the default browser.

If you are running Firefox 40 Stable you may want to check for updates right away to download and install those.

While you may not be affected by the issues directly, it is usually better to run the latest version of the browser.

To check for updates manually, tap on the Alt-key on your keyboard and select Help > About Firefox from the menu that opens up at the top of the browser interface.

Firefox runs a manual check for updates. If it finds any, it will download and install the latest provided that you have not modified the update settings of the browser.

A restart is required to complete the process.

Now You: Have you noticed issues in the latest version of Firefox?


Mozilla releases Firefox 40.x updates to fix issues in the browser
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Mozilla releases Firefox 40.x updates to fix issues in the browser
Mozilla released Firefox 40.0.2 days after it released Firefox 40 to fix several issues in the web browser.

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  1. John S said on September 24, 2015 at 6:08 am

    All versions of FF from v39 onward crash and burn when attempting to open MAFF archival files previously saved with FF. Have gone back to v39.

    Win 7 SP1, 32 bit. Latest v of MAFF.

    I see others are also reporting the same MAFF bug.


  2. Razzle said on August 26, 2015 at 6:20 pm

    FF 40.x broke my mouse. Had problems with the mouse registering 2 clicks when single-clicking, even in other apps besides FF. Also, the space bar on my keyboard would register a space, then immediately follow with a backspace, resulting in all my words being typed with no spaces between them.

    The only thing that worked for both issues was completely removing FF from my computer (Win 7 64-bit). This is bad, because some websites I use don’t work in IE, only in FF.

  3. Mikefellh said on August 25, 2015 at 6:37 am

    FF40.0.2 sure has been crashing on the MAC!!!! If I didn’t do anything it would be fine, but as soon as I did anything with it FF would just freeze up. Did all the usual things, closing tabs, refreshing FF, running in safe mode, reinstalling FF…it wasn’t until I DOWNGRADED to 39.0.3 that everything was working as smoothly as it was before the STUPID 40.0.2 upgrade!!!!

  4. Carl said on August 20, 2015 at 10:47 pm

    My FF crashes started after installing Win 10.

    Nearly every time I use the “close” X (top right) FF crashes.

    When will there be an update to fix this???

  5. Dee said on August 20, 2015 at 5:32 am

    When I try to restart after updating to FF40.0.3, it freezes up. OK, I admit I have 100’s of tabs open. But in FF39 it wasn’t generally a problem — when it re-instated a session, it would keep tabs inactive until I clicked on them. In FF40.0.3, it seems like maybe it is trying to activate them all, which eats up all my 16 GB of RAM. Not good! (I am using Mac OS X 10.7.5, by the way.)

    1. Dee said on August 20, 2015 at 5:48 am

      Epilogue: Ok, I’m finally up and running, after 3 tries. Turned out the session I was trying to restore had 2 open windows, one with 100s of tabs, one with only one. When given a “Restore Session?” window which showed all tabs and both windows, I unchecked the window with one tab, and after that the session restored okay. (I have always found that having more than one window open (at least when one of them has a zillion tabs) will make it difficult to successfully restore a session.) I’m now back to having 10+ of my 16 GB of RAM free. But maybe I should consider pruning back the number of open tabs…. one of these days.

      We’ll see how it goes. Inauspicious beginning, but I have faith. Had to post these posts from Safari, but now I’m going back to FF, my favorite browser.

  6. Amezzay said on August 19, 2015 at 10:55 pm

    The browser freezes after updating to 40.0.0. It continue to freeze after updating to 40.0.2
    I’m running Windows 7.
    Thank you for your help

  7. Carl said on August 19, 2015 at 10:43 pm

    Clicking on “close” X on the top right to close a page crashes FF 40.0.2 approx 90% of the time.

  8. Gemma said on August 19, 2015 at 5:50 pm

    Updated 08/19 using Windows 10 Home and the minimize, expand and close buttons on the top right no longer highlight when moused over or click. I’m right clicking to close as a workaround for now.

  9. nick said on August 18, 2015 at 10:04 pm

    Having some issues with Facebook since I updated Firefox 18/8/15

  10. Otto said on August 18, 2015 at 9:41 pm

    On Linux Mint Mate, the update to firefox 40 results in totally empty screens.

  11. P.Larkin said on August 18, 2015 at 5:09 am

    two thumbs down on 40.0.2…
    I’ve been using theme Nautipolus for years. 40.0.2 apparently broke it…. It says it is running, but the UI looks like “factory OEM” firefox.
    Win 8.1

  12. MLinneer said on August 18, 2015 at 1:46 am

    On OS X 10.10.5, Firefox 40 is the worst I’ve used in a long while. It now eats more RAM and battery than Chrome. Videos often fail to load, both Flash and HTML5, and when they do load my fans will come on after a few minutes. It still has that persistent memory bug where it won’t release once memory gets over 600Mb. I’m pretty much a single tab browser, occasionally Cmd-clicking a second tab to read another link, but even that over time will eat up to 2Gb of RAM. I don’t have any add-ons and the only extension installed is Flash. Everything is update, fresh profile, and even fresh install of Firefox. It really used to be a nice browser… just not anymore.

  13. Carol said on August 17, 2015 at 10:36 pm

    I still have the startup crash repport with the 40.0.2 version. I´ve installed it twice and I haven´t any success.
    Could you please help me with this problem? I have already read all the comments of this bug (Bug 1160295) and it seems it´s still not solved.

  14. Brian said on August 17, 2015 at 12:44 pm

    i have just updated to 40.0.2 in our office and all machines cannot select from drop down boxes. Clicking the box activates the drop down, but the selection will not select, although it can be selected by hitting “enter” on keyboard

    1. Carlos said on August 19, 2015 at 12:23 pm

      Here we have the same issue.
      Just to bring you some light:
      In our case there was a script attaching a mouseUp event to the entire document that crashes the built in behavior on selects.
      Probably before firefox 40 that document attached event was not propagating to selects or that event was overridden somewhere, the fact is that we restrict the event to the element that really need that and the bug was solved.

      1. Richard said on August 25, 2015 at 10:21 am

        Unfortunatelly, I have no chance to operate with behaviour of elements, because AjaxControlToolkit is a black box. Don’t you know what was exactly changed in this FF version?

    2. Richard said on August 19, 2015 at 9:31 am

      I have the same problem, but only in dropdowns inside the ModalPopupExtender control (MS’s AjaxControlToolkit). No idea how to solve it. It is quite unpleasant, customers have to downgrade.

    3. Richard said on August 18, 2015 at 12:09 pm

      Yes, the same here.

    4. Mohan Kumar BS said on August 18, 2015 at 10:09 am

      I ‘m also facing the same issue, selection through the mouse is not working after a click and we have to hit Enter to get selected with the value.

      Could you please provide the solution and its urgent

      Mohan Kumar BS

    5. mike said on August 17, 2015 at 7:22 pm

      Brian, the same here, we can open dropdowns but not select an option via clicking it. Some dropdowns exhibit this behavior while others do not

  15. BobP said on August 16, 2015 at 11:26 pm

    After installing FF 40.0.2 I cannot add a bookmark from the menu or from right clicking. Nothing happens when clicking on the add bookmark.

  16. Anonymous said on August 16, 2015 at 10:10 pm

    I got firefox-40.0.2.tar.bz2 with Flash FXP off the new FTP server. However, it seems that the win 32 builds are all “550 Permision Denied”
    Anyone else having this issue?

  17. J Mc said on August 15, 2015 at 3:33 pm

    After the update to firefox 40.0.2 web browser, to view live streaming, the live stream freezes…………I changed the browser to google chrome and no problem……….

  18. Baz said on August 15, 2015 at 2:06 pm

    Some Videos will not play on various web-sites….always have to clear cache to get them to play

  19. Eva said on August 15, 2015 at 10:27 am

    I just installed the latest test version of TMP found here: and that seems to have fixed the Bookmark All Tabs problem. The Bookmark menu is now back to the old two-line version.

    1. The Phantom Electron said on August 16, 2015 at 9:28 pm

      THANK-You !!! It has been a VERY long week bookmarking everything one at a time…. Although I had to install the developer version Version —the regular channel one did not fix the problem…. this week is now going to be sooo much nicer!!!!! ………………………

  20. j said on August 15, 2015 at 9:34 am

    I hit the same problem with Bookmark all Tabs in FF 40. In my case, its the fault of the Tab Mix Plus extension and I’ve just disabled it for now.

  21. Ovidiu said on August 15, 2015 at 7:00 am

    Problem for me is Youtube videos only in 360p and not allow to change in 720p or 1080p.. verry verry annoying.

    1. dashie said on August 27, 2015 at 10:21 am

      Same here, 360p only qq

  22. Rick said on August 15, 2015 at 3:35 am

    cntl+shift+D = bookmarks for me

    It is likely that one of your plugins has taken over the shortcut without checking to see if it was already reserved.

    Since you are using TMP, pop into addons via the hamburger / TMP options / menus / shortcuts and reset the tab shortcuts. If they look right, change them and save, then pop back in to set them back to what you want. This should override whatever other plugin may have taken the shortcut.

    1. Jojo said on August 15, 2015 at 9:21 am

      Maybe a screenshot will better help see what I am trying to describe:

      The Bookmark menu comes up but selecting a folder does not work. Maybe someone can try what I am doing to see if it works for you?


      1. Frank said on August 17, 2015 at 12:35 am

        I had the same problem with Ctrl-Shift-D as Jojo so beautifully described. For me the cure was disabling Add Bookmark Here ². There are reported FF 40+ troubles with it as discussed at

      2. Jojo said on August 15, 2015 at 10:27 am

        I just reverted to 39.0.3 to test further. It still works fine there. This is how it is supposed to look / work:

      3. Eva said on August 15, 2015 at 9:57 am

        The same thing has been happening for me since the update to FF 40.x.

        Also, just opening the New Bookmarks menu creates an empty folder for me, even if I click Cancel instead of Add Bookmarks.

        ETA: It works fine in Safe Mode.

      4. Martin Brinkmann said on August 15, 2015 at 9:29 am

        JoJo, I don’t have that issue in vanilla Fx 40.0.2. Can you try running Firefox in Safe Mode (hold down Shift on start), to make sure this is not caused by an add-on?

  23. Jojo said on August 14, 2015 at 9:24 pm

    Mozilla has screwed up the 40.x release of FF. There are at least 2 bugs that I have noticed so far:

    1. F11 (full screen) does not hide the tabbar any longer. In fact, in my system, the tabbar is about 5 lines ABOVE the bottom of the screen and those 5 lines below are just blank (gray). I am running TMP for tab management.

    2. Ctrl-Shift-D no longer appears to work to save tabs. The menu is messed up and creates an entry called “new tab” with nothing in it. I have made multiple attempts to try to get it working without success.


    1. Rick said on August 14, 2015 at 11:51 pm

      Not having a problem with F11 and the tab bar. Also using TMPv

      Ctrl-shift-D? When you say save tabs, do you mean bookmark, or something else like creating a .maff of the page.

      1. Jojo said on August 15, 2015 at 1:29 am

        I mean bookmarking tabs. I’ve done this manually every day for years as FF sometimes loses tabs on a crash and I tend to keep 50-70 tabs open at any time.

        Both of these functions worked fine in FF 39.x for me. They stopped working correctly in 40.x. If that is a fault of some add-on mixture now, then it is still something that FF created.

  24. jamie said on August 14, 2015 at 7:08 pm

    Bookmark all Tabs doesn’t work for me anymore.
    Whenever I rightclick on a tab and click bookmark all tabs a new bookmark folder is created but it’s empty.
    Strg+Shift+D opens a dialog to create a new tab, but this is the official shortcut to bookmark all tabs

  25. wybo said on August 14, 2015 at 5:53 pm

    Running on 8.1 I did not encounter any problems with 40.0.

    I never get a notification. Usually I get the notification from Glary Utilities.

    Funny how the “Security Advisories For FireFox” does not mention 40.0.2 (yet)

    1. Rick said on August 14, 2015 at 6:31 pm

      No security advisory would have been issued as the changes are not security related. The update only fix rare crashes, that as you have noted, didn’t impact your system.

      1. wybo said on August 15, 2015 at 1:58 pm

        Ah yes that makes sense. Thanks.

  26. Rick said on August 14, 2015 at 5:07 pm

    The ftp site has an interesting README file that says:

    The contents of has moved to

    So long and thanks for all the fish! The end of ftp support in FF is soon at an end :(

    1. ams said on August 14, 2015 at 5:51 pm

      Rick, “end of ftp support” is incorrect.

      Nothing changed except the URL. The entire content is still available via FTP protocol

      1. Joker said on August 15, 2015 at 9:01 am

        @Martin Brinkmann
        Considering the decisions Mozilla made in the last two years, I don’t have the same confidence as you do. ;)

      2. Rick said on August 15, 2015 at 3:26 am

        You will also find a 550 permission error on this url too :) or :(

      3. Rick said on August 14, 2015 at 10:58 pm

        The final decision hasn’t been announced but I don’t think that this change is just a coincidence either.

        I give it to FF42; I agree it won’t be in the next few months.

      4. Rick said on August 14, 2015 at 7:12 pm

        Actually, FTP support is coming to an end, but it that is an entirely different issue. (

        The fact that the README file they have on the ftp site refers you to http, is one of the first steps on dropping ftp.

        How strange it would look if they said “FTP in FF is no longer supported” and they still had their downloads sitting on a FTP server?

      5. Martin Brinkmann said on August 14, 2015 at 7:41 pm

        Rick this is being discussed but the decision to remove ftp support has not been made. While it is certainly a possibility, I find it highly unlikely that Mozilla would go ahead with it at this time.

  27. fppfps said on August 14, 2015 at 4:27 pm

    The update changed the loading icon from green to blue and it broke a small plugin (Open Tabs Next to Current) but other than that nothing major.

    1. Larry said on April 3, 2016 at 3:40 am

      , have you noticed window collapsing to half screen when toggling tabs?

  28. Yuliya said on August 14, 2015 at 2:43 pm

    I did get prompted to update it this morning, as I have set to just check for updates and let me choose what to do. I thought it was some security issue. Ah well, I didn’t have any problems with FireFox lately.

  29. michaelpaul said on August 14, 2015 at 2:32 pm

    Had no problems before update or after updates
    didn’t affect me at all.
    But whatever problems that was encountered by some always update
    to recent versions

  30. Tom said on August 14, 2015 at 2:25 pm

    Neither any issues nor I think the ones above listed would affect me but of course as you say it is usually best to run the latest version of the browser.

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