Add-ons disabled or failing to install in Firefox

Incident summary

Updates – Last updated 14:35 PST May 14, 2019. We expect this to be our final update.

  • If you are running Firefox versions 61 – 65 and 1) did not receive the deployed fix and 2) do not want to update to the current version (which includes the permanent fix): Install this extension to resolve the expired security certificate issue and re-enable extensions and themes.
  • If you are running Firefox versions 57 – 60: Install this extension to resolve the expired security certificate issue and re-enable extensions and themes.
  • If you are running Firefox versions 47 – 56: install this extension to resolve the expired security certificate issue and re-enable extensions and themes.
  • A less technical blog post about the outage is also available. If you enabled telemetry to get the initial fix, we’re deleting all data collected since May 4. (May 9, 17:04 EDT)
  • Mozilla CTO Eric Rescorla posted a blog on the technical details of what went wrong last weekend. (May 9, 16:20 EDT)
  • We’ve released Firefox 66.0.5 for Desktop and Android, and Firefox ESR 60.6.3, which include the permanent fix for re-enabling add-ons that were disabled starting on May 3rd. The initial, temporary fix that was deployed May 4th through the Studies system is replaced by these updates, and we recommend updating as soon as possible. Users who enabled Studies to receive the temporary fix, and have updated to the permanent fix, can now disable Studies if they desire.For users who cannot update to the latest version of Firefox or Firefox ESR, we plan to distribute an update that automatically applies the fix to versions 52 through 60. This fix will also be available as a user-installable extension. For anyone still experiencing issues in versions 61 through 65, we plan to distribute a fix through a user-installable extension. These extensions will not require users to enable Studies, and we’ll provide an update when they are available. (May 8, 19:28 EDT)
  • Firefox 66.0.5 has been released, and we recommend that people update to that version if they continue to experience problems with extensions being disabled. You’ll get an update notification within 24 hours, or you can initiate an update manually. An update to ESR 60.6.3 is also available as of 16:00 UTC May 8th. We’re continuing to work on a fix for older versions of Firefox, and will update this post and on social media as we have more information. (May 8, 11:51 EDT)
  • A Firefox release has been pushed — version 66.0.4 on Desktop and Android, and version 60.6.2 for ESR. This release repairs the certificate chain to re-enable web extensions, themes, search engines, and language packs that had been disabled (Bug 1549061). There are remaining issues that we are actively working to resolve, but we wanted to get this fix out before Monday to lessen the impact of disabled add-ons before the start of the week. More information about the remaining issues can be found by clicking on the links to the release notes above. (May 5, 16:25 EDT)
  • Some users are reporting that they do not have the “hotfix-update-xpi-signing-intermediate-bug-1548973” study active in “about:studies”. Rather than using work-arounds, which can lead to issues later on, we strongly recommend that you continue to wait. If it’s possible for you to receive the hotfix, you should get it by 6am EDT, 24 hours after it was first released. For everyone else, we are working to ship a more permanent solution. (May 5, 00:54 EDT)
  • There are a number of work-arounds being discussed in the community. These are not recommended as they may conflict with fixes we are deploying. We’ll let you know when further updates are available that we recommend, and appreciate your patience. (May 4, 15:01 EDT)
  • Temporarily disabled commenting on this post given volume and duplication. They’ll be re-enabled as more updates become available. (May 4, 13:02 EDT)
  • Updated the post to clarify that deleting extensions can result in data loss, and should not be used to attempt a fix. (May 4, 12:58 EDT)
  • Clarified that the study may appear in either the Active studies or Completed studies of “about:studies” (May 4, 12:10 EDT)
  • We’re aware that some users are reporting that their extensions remain disabled with both studies active. We’re tracking this issue on Bugzilla in bug 1549078. (May 4, 12:03 EDT)
  • Clarified that the Studies fix applies only to Desktop users of Firefox distributed by Mozilla. Firefox ESR, Firefox for Android, and some versions of Firefox included with Linux distributions will require separate updates. (May 4, 12:03 EDT)

Late on Friday May 3rd, we became aware of an issue with Firefox that prevented existing and new add-ons from running or being installed. We are very sorry for the inconvenience caused to people who use Firefox.

Our team  identified and rolled-out a temporary fix for all Firefox Desktop users on Release, Beta and Nightly. The fix will be automatically applied in the background within 24 hours. No active steps need to be taken to make add-ons work again. In particular, please do not delete and/or re-install any add-ons as an attempt to fix the issue. Deleting an add-on removes any data associated with it, where disabling and re-enabling does not.

Please note: The fix does not apply to Firefox ESR or Firefox for Android. We’re working on releasing a fix for both, and will provide updates here and on social media.

To provide this fix on short notice, we are using the Studies system. This system is enabled by default, and no action is needed unless Studies have been disabled. Firefox users can check if they have Studies enabled by going to:

  • Firefox Options/Preferences -> Privacy & Security -> Allow Firefox to install and run studies (scroll down to find the setting)

  • Studies can be disabled again after the add-ons have been re-enabled

It may take up to six hours for the Study to be applied to Firefox. To check if the fix has been applied, you can enter “about:studies” in the location bar. If the fix is in the active, you’ll see “hotfix-update-xpi-signing-intermediate-bug-1548973” in either the Active studies or Completed studies as follows:

You may also see “hotfix-reset-xpi-verification-timestamp-1548973” listed, which is part of the fix and may be in the Active studies or Completed studies section(s).

We are working on a general fix that doesn’t use the Studies system and will keep this blog post updated accordingly. We will share a more substantial update in the coming days.

Additional sources of information:

421 comments on “Add-ons disabled or failing to install in Firefox”

  1. mach wrote on

    Does not work for me either on my default User Profile (the ones where the extensions have been disabled). Also, I cannot even view the “about:studies” page with my default User Profile.

    When I create a new User Profile, I can install the disabled extensions (and view the “about:studies” page). Of course, this defeats the purpose of keeping Firefox at all (which I would still love to do, though).

    Do I have to wait for my default User Profile to get the hotfix-reset-xpi-verification-timestamp-1548973 study, while a new User Profile gets it at once?

    I am using the latest 66.0.3 release.

  2. Boris wrote on

    still nothing works, version 66.0.3

    hotfix-reset-xpi-verify-timestamp-1548973 • Complete

  3. delaus wrote on

    It works after two restarts. Thank you.

    Windows 10, Firefox 66.0.3 (64bit)

  4. Chris wrote on

    Any help with the Android version? I’m sure you guys are working on it, thanks for giving up your Saturday, whomever is doing so.

  5. Jack wrote on

    I’m using Firefox for Android v66.0.2 and there are no studies section within settings or privacy.
    Is there a workaround for Android?

  6. finitek wrote on

    Currently running FF 66.0.3 (64-bit)

    All of the hotfixes are in place and all add-ons are still disabled. The fix doesn’t appear to be working properly.

    This study sets app.update.lastUpdateTime.xpi-signature-verification to 1556945257.

    This is a hotfix that updates an intermediate certificate used for signing add-ons. It is one of the mechanisms used to fix bug 1548973.

    All add-ons are definitely still toast.

  7. lg wrote on

    I have Firefox 66.0.2 on my mobile and didn’t update anything and have all auto updates disabled but earlier ublock origin crashed and quit due to this issue. With nothing updating how and why did this happen?

  8. lleosiid wrote on

    What if I don’t see the “hotfix-update” thing in the about:studies page? Does it show up on its own or do I need to do something to activate it?

  9. Bruce wrote on

    This disabled my dissenter extension. How do I get it back? No studies active.

  10. john wrote on

    im on 66.0.3 and under studies shows these



    are these normal? still all addons disabled. hope settings dont get messed up

    1. Kev Needham wrote on

      You’ll need the “hotfix-update-xpi-signing-intermediate-bug-1548973” for the fix to be applied. Firefox should download and apply it shortly.

      1. Leon G wrote on

        howcome, of my 3 pc’s in home, all 3 running 66.0.3 (64bit), only one of them has the hotfix-update study completed, and the other 2 only have the hotfix-reset in the studies…; it doesnt make sense to me. instead of waiting on the hotfix-update, is there a location where we can dwnld and apply this right now ?

      2. john wrote on

        this has been for over 5 hours….if every study needs 6 hours and i need another one then good luck tomorrow for me

      3. Paul Farmer wrote on

        It is now almost noon, May 4, and no hotfix update study is active on my computer. Studies are enabled. How about providing some further communication. FireFox has now enabled numerous advertising and tracking cookies on my computer.

  11. Michael Downey wrote on

    Still no fix in sight for Android users who don’t have this feature. What’s the plan?

    1. Kev Needham wrote on

      A separate release of Android that addresses this is being prepared. We’ll update the post and on social when it’s available.

  12. Clpos wrote on

    Add-ons are STILL DISABLED after “hotfix-update-xpi-signing-intermediate-bug-1548973” study is completed.
    My Firefox latest Version is Firefox Quantum 66.0.3

  13. Gabriel wrote on

    This no work for me because Nighly no open after the last udpate of yesterday

  14. Sunset wrote on

    version 59.9.0 (32 bit) windows vista version still not fixed

  15. Cjay wrote on

    OK received “hotfix” update!!

  16. Michael Negranol wrote on

    The option “Allow Firefox to install and run studies” does NOT remain active once selected. Navigating away from options and reopening them or refreshing the option’s page renders the option unchecked. The about:studies page specifically states “No new studies will run.”

    I am running Firefox version 66.0.3 (64-bit)

    1. Michael Negranol wrote on

      Fixed it – the app.normandy settings in about:config were the key. Making sure everything was enabled and the first run set to true was what was necessary.

      My addons are now restored, and Firefox, and, by extension (no pun intended), for all intents and purposes, the internet is working again.

  17. Joseph Le Petomane wrote on

    “Canadian Mozillian working to make Add-ons in Firefox awesome.”

    Awsomely incompetent you mean. FF 66.03. I enabled studies, still nothing. Chrome may come from the Spawn of Satan, but at least they know their rear end from a hole in the ground.

    1. Kev Needham wrote on

      It can take up to six hours for Firefox to load and apply the study.

    2. Igor Jerosimić wrote on

      Try to restart Firefox, for me all studies loaded immediately after restart.

  18. Borek wrote on

    Firefox 66.0.3, Studies enabled, can’t see “hotfix-update-xpi-signing-intermediate-bug-1548973” in Active nor Completed however.

    1. Kev Needham wrote on

      It can take up to six hours to be loaded, you should see it in short order.

      1. Nerida wrote on

        6 hours from when, please? I can’t find the time of your original post.

        1. Calchung wrote on

          Open about:config and change “app.normandy.run_interval_seconds” from 21600 to 1

  19. buki wrote on

    Firefox just disabled all my add-ons. I thought this issue was already fixed but it just started on my browser. I have the latest version of firefox on Windows 7.

  20. Daniel wrote on

    Using 60.6.1esr (64-Bit) I have no option to activate or deactive studies in the settings. Any other option?

  21. sligthlyannoyedFirefoxuser wrote on

    I was running Firefox 66.0.3 on Windows 10 today, then suddenly ca. 90 % of my add-ons were disabled by Firefox/Mozilla, including NoScript and uMatrix, because they couldn’t be verificated or something (I’m using the german version). Searching für updates didn’t help.

    Then I noticed that a RC for 66.0.4 was aviable, so I installed that one. Most add-ons were re-enabled again, but some were not, including Tree Style Tab and Request Control.

    I tried unsuccesfully to re-install Tree Style Tab from (failure during install), because there is a new vesion 3.0.11. Then I downloaded the XPI file and drag-and-droped it on the add-ons page in Firefox, but Firefox says the add-on is damaged ??? WTF…

    I tried the same procedures with Request Control, with the exact same results…

    So how can I install the new version of Tree Style Tab? And why exactly this add-on has been disabled in the first place?

    The others add-ons that remain disabled are Toggle Referrer, Smart HTTPS and Dark Reader.

  22. Gabriela wrote on

    I can’t even start Nightly, so no way to to enable studies!
    I either get a yellow window with a message about a XML error with a Chrome location that stays open, or the same window that closes after a few seconds.
    I would greatly appreciate some help!!!

  23. Jack wrote on

    What about mobile?

  24. Richard wrote on

    Both Hotfixes have been applied in my Study history. (Latest one: hotfix-reset-xpi-verification-timestamp-1548973 ) The Hotfix is marked as complete. Yet, I can neither change the language of my firefox nor can I use any Add-ons. Do I need to wait up to 6 hours even after the Hotfix is marked as completed?

  25. Unhappy wrote on

    You’ve to break your privacy preferences in order to get a fix… Mozilla people can’t you just publish an updated version or tell people which file has to be recovered from a previous backup?

  26. Tadas Balaišis wrote on

    I’ve got studies disabled and I’m not going to enable it. My add-ons became disabled without studies and I expect them back same way (without studies as a tool). How can I have my add-ons back? Can I revert to the older version? Can Mozilla release common update like a newer version, but in fact downgrade to the good old version?

  27. LMG wrote on

    I keep using version 56.0.2 (64-bit) because I want to use some legacy add ons that make my life easier. I appreciate your efforts but I still do not want to lose more of my choices, isn’t that what open source should be? My anti-virus and firewall WOT and Adblock plus keep me safe. If I make the wrong choices, I will pay for it.

  28. Ivo wrote on is this the right study? can I still wait six hour? all addons still disabled

  29. Reece wrote on

    How do we get this bugfix without also agreeing to participate in other “studies” that may be going on concurrently?

    Requiring users to allow other “studies” to get a bugfix is unacceptable.

  30. Mai De Leon wrote on

    I have it as active but still my add-ons are not working. Why? I’m running on Win10 with the latest Firefox.

  31. chas wrote on

    Why should we have to enable your data capture feature and allow you to use our information so you can fix the thing you broke.

    It is off for a very good reason, release a new version of firefox with the fix. Until this happens I will no longer use your software.

  32. David wrote on

    It looks as though we may need to reinstall our add-ons again after the hotfix is installed, as “Check for updates” doesn’t seem to do the trick? The existing add-on settings appear to be retained, however, at least.

    (NB: I’m using Firefox ESR if this makes a difference (partly to avoid ever-shifting quicksands, ironically))

  33. Bruce wrote on

    And also disabled Lastpass extension. 🙁

  34. John wrote on

    Will the ESR version of FF receive the update?

  35. Si2Bim wrote on

    Working on Firefox 62.0.3 (64Bit)

    Holding on to this version for the sake of “SAVE AND END” feature…. 🙂

  36. Robert wrote on

    I can’t use my add-ons . Please fix Firefox. I wish I had unchecked automatic update.

  37. Mac User wrote on

    I can’t enabled studie on Mac, when i checked studie, refresh setting page reset it to unchecked.
    but no problem my windows machine.

  38. Disgruntled_and_tired_user wrote on

    Add-ons still not working. With Adblock being disabled Firefox is unusable due to ads being everywhere. Will switch to a browser that actually works in the meantime.

  39. MCtoo wrote on

    66.0.3 (64-bit) Quantum. Win 10 Pro
    Nothing happened. I only have Ad-Blocker and Midnight Crescent Moon by MaDonna installed.
    Both are still disabled.

    This is a hotfix that updates an intermediate certificate used for signing add-ons. It is one of the mechanisms used to fix bug 1548973.

    Looking at config, I was curious if this fix also added xpinstall.signatures.required false.
    It was set to true before.

    This is still running, but config shows the correct timestamp “Value”.
    This study sets app.update.lastUpdateTime.xpi-signature-verification to 1556945257.

    I have shut down FireFox and restarted it several times. Still nothing…

    1. MCtoo wrote on

      I noticed this in another post above”dom.push.alwaysConnect was setted to “true” in abot;config.”
      Is this required?
      Mine is set to false,

  40. Primatebuddy wrote on

    Applied the requisite preferences, restarted the browser, and the study appeared, as well as my extensions.

  41. Nerida wrote on

    6 hours from when? I can’t find the time of your original post.

  42. Mark wrote on

    Have 66.0.4 and not fix yet

  43. adam wrote on

    this sucks big time, but thanks for working towards a fix quickly. i believe in firefox

  44. Herbert wrote on

    Studies disabled in user.js, will leave it that way.

  45. Andy wrote on

    I have “hotfix-reset-xpi-verification-timestamp-1548973 – active”, but still add-ons are disabled and I can not enable any new one. What’s wrong? Is it normal?

  46. Hey wrote on

    It worked. Took it about 5 minutes.

  47. ESR wrote on

    ESR 60.6.1esr (32-Bit) does not have “studies”.

    Are ESR users left out again ?

  48. Philip wrote on

    I’m getting “hotfix-reset-xpi-verification-timestamp-1548973•Complete” but still can’t install add-on AdBlock Plus. it’s 11:18 EDT.

  49. Rheuji17 wrote on

    I got most of my add ons back except for the Firefox sync

  50. JumpStart1717 wrote on

    I just went and checked to make sure the hotfix was active and all my add-ons reloaded! Thank you for the help.

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