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. srs06 wrote on

    Just updated for me (Windows 7). All the add-ons are now enabled but I had to reset the old theme manually (no big deal).

    Thanks for the fix.

    1. srs06 wrote on

      I should have added: 66.0.3 (64-bit)

    2. Sean wrote on

      I don’t see the hotfix on my laptop yet. Do I just need to uncheck the box and wait several hours, or do I need to restart my laptop?

  2. David wrote on

    The six-hour wait can be dropped to seconds if you temporarily change the value of “app.normandy.run_interval_seconds” in about:config, restart, and then change it back to 21600 (six hours) after things are working.
    (It would be nice if you’d approve this comment, Kev.)

    1. HellOverHeresy wrote on

      Searched “about:config” but couldn’t find setting called “app.normandy.run_interval_seconds”.

    2. Lucas wrote on

      Awesome, that worked perfectly! Thanks!

    3. aswiran wrote on

      ty this already my answer question which still need moderation~
      really helpful

    4. Chris James wrote on

      Sadly this didn’t even work for me. Still no second update in there, just one.

      1. Chris James wrote on

        David – any other things that need to be changed but that? I changed mine from 21600 to 5, and nothing changed for me.

    5. JohnG wrote on

      Change the value to zero?

      Also, are the timestamps associated with these posts PDT? or some other time zone?


    6. Yury wrote on

      The trick with run_interval_seconds works, thank you, David.

    7. MCtoo wrote on

      Thanks for the suggestion. I tried 5 and 60. Neither worked.
      66.0.3 (64-bit) Quantum. Win 10 Pro Desktop

    8. HotShot wrote on

      YES YES YES!

      I changed the value from 21600 to 60 and restarted FF.

      The studies are now listed:
      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 my add-ons are back and working!!!
      I have changed the value back to 21600.

      Many, many thanks!

    9. GK wrote on

      Thanks for the tip.
      I put ‘normandy’ in the filter at the top of the page to easily see the field.
      The good thing about this is that once it kicked in, it added several more items of the form app.normandy to the list, so I knew it had run.

    10. Mark wrote on

      Worked for me too thank god. I was about to ask how long the rollout would take and what kind of sequence Mozilla was using to determine who got the rollout first and who got the rollout later. David, much thanks for posting this hack!!!

    11. Jacques Amar wrote on

      Thanks for the tip. Somehow, a few of my extension were uninstalled with this study :-/

    12. Cole wrote on

      Nice work David. Kev might not have approved this comment yet, but I certainly will. Took all of 1 minute, and all Add Ons are enabled again. Brilliant! Thanks.

  3. FaceActor14 wrote on

    ✓ had 8 “legacy” extensions disabled arbitrarily
    ✓ read several “support” and “discourse” threads
    ✓ advised of temporary “solutions”
    ✓ xpinstall.signatures.required (already) set to “false”
    ✓ hotfix extension installed and enabled
    ✓ “legacy” extensions still not functioning
    ✓ digital ecomony suffers ~20% loss
    ✓ awaiting permanent resolution
    ✓ pissed af

    1. FaceActor14 wrote on

      I forgot one:

      ✓ enabled “studies” in privacy settings

      1. FaceActor14 wrote on

        (outcome remains the same)

    2. the GhostPony wrote on

      I hear ya. This hit me early this morning at about 1AM while I was online doing research. I was NOT happy. Still aint.

  4. Derdada wrote on

    ESR does not have “studies” to enable

    1. Dennis wrote on

      Are you using Windows? I have the Mac Firefox 60.1esr version and it is there, but unfortunately just shows “You have not participated in any studies.”

  5. ben wrote on

    I have turned back on the studies
    and only a completed one appears:

    the active studies is emplty
    I run
    66.0.3 (64 bits)

  6. Jacques Le Roux wrote on

    Will it work with version 56.0.2 ? Thanks

  7. Myles wrote on

    What about Firefox on Android? The studies option doesn’t even exist for us.

    1. Eric wrote on


    2. VulcanTourist wrote on

      Firefox on Android wasn’t affected, according to what I read last night.

  8. No privacy wrote on

    This forces every user around the globe to share their data collection even though they’ve previously chosen to not do so. Nice move.

    1. Can’t Melt Steel Beams wrote on

      Well there is an alternative for the uber patient. Simply wait for the next Firefox update.

  9. Momodora wrote on

    So I don’t need to enable the Studies and just wait?

    1. Chiv wrote on

      When I enabled Studies, my extensions reappeared within a few seconds. The damage is done though. Mozilla really should provide a comprehensive clearly understood way of disabling all this rubbish designed to allow companies to remotely collect data and remotely mess with things on our computers and devices. “Normandy” means nothing to most users, and that’s how they want it. Disgraceful.

  10. bxm wrote on

    Where are my valuable Firefox Multi-Account Containers? They seem to have been erased / reset to installation default values. Everything gone! You killed your very own extension, WTF, Mozilla?

  11. Drakk wrote on

    Does this apply to older Versions of Firefox aswell? I’m bound to the last non Quantum Release of Firefox.

  12. Francis wrote on

    Thank you.

    Ad-ons started working immediately after enabling Studies and restarting Firefox.

    Would appreciate if Firefox doesn’t roll out anymore drastic updates in the future.

    Will continue to support Firefox, thanks!

  13. mge wrote on

    Still nothing here. Firefox 66.0.3 (64-bit), Windows 10. No “hotfix-update-xpi-signing-intermediate-bug-1548973” under “about:studies”.

    I reckon all there is to do is wait and hope. If I come back in 3 MORE hours and still nothing, then I’ll check back here to see what’s what.

  14. Jakob wrote on

    Is this actually serious?

    A major screw up and the proposed solution is to manually re-enable Studies, a feature that requires users to check “Allow Firefox to send technical and interaction data to Mozilla”?

    I bet they know that half the users will forget to return to their previous configuration. AFAIK they pushed ads through this “studies” feature in the past, I think for some movie. (“Mr. Robot”?)

    I use firefox on all devices, but this is really a toxic company.

  15. Solomon Ford wrote on

    It is unacceptable to require us to enable sending “technical and interaction data” (whatever that might mean) just so we can get a version of the browser that actually works. I’d rather use another browser instead.

    Maybe next time just fix the downloadable versions on your website so we aren’t forced to enable this odd and unrelated feature to get bug fixes.

  16. theGhostPony wrote on


    Geezus, you ppl really screwed this up royally and now we have to wait “days” while our system’s security is compromised. Good lord.

  17. Dennis wrote on

    Allow studies has always been enabled but when I go there I see: “You have not participated in any studies.”


  18. Claudia wrote on

    I have a curious issue that maybe can help. I have two Firefox versions on my phone, v. 66.0.2 for Android and the latest Beta version.
    The first one has not been affected at all by this problem, while the Beta is!

  19. pastedpaper wrote on

    The fis isn’t complete… With Adblock plus, the icon and the cheks (in the options) have disappeared… there is an empty space for the icon, in the bar, but with no picture anymore…

    1. pastedpaper wrote on


    2. pastedpaper wrote on

      looks like everything’s fine now

  20. Shadow wrote on


    My computer browser was not one of the ones affected, but my android mobile device was. I noticed that the hot fix says it is for “Desktop users on Release, Beta and Nightly” only and I have not seen any mention for Android mobile device fixes.

    I was wondering if there is any word on a fix for those. Any information would be appreciated, thank you.

  21. Private wrote on

    I do not consent to the data collection and use and thus can’t enable the boxes “Allow Firefox to send technical and interaction data to Mozilla” or “Allow Firefox to install and run studies”.

    How and when do I get my extensions working?

    They are important for retaining my privacy and I am horrified to be suddenly notified that all of those addons have been disabled.

    Please work on the fix ASAP because I do not consent to your data policies and thus can’t enable the “studies” option.

    Addons that Mozilla disabled for me:

    – Cookie AutoDelete
    – Decentraleyes
    – HTTPS Everywhere
    – NoScript
    – uBlock Origin

  22. Emre wrote on

    Addons are still not working. 🙁 66.0.3 (64 bit)
    I’ll try Force delete FireFox same problem… I tried to install Adblock, i get the connection error.

  23. J Sneably wrote on

    Is there a way to just manually force this update instead of sitting on our thumbs waiting for 6 hours?

  24. L.Roscoe wrote on

    I had studies disabled, re-enabled it a half hour ago. The indicated study still has not shown up. Is there a way to pull it?

  25. Luther wrote on

    I can’t even turn on the ‘Allow Firefox to install and run studies’ option in preferences, the box doesn’t stay ticked when I click it and come back to check.

  26. Mary wrote on

    Do I have to turn on “Allow Firefox to install and run studies” for all my computers for this fix or are you guys fixing it automatically now? Btw, I like and use the older version 56.0.2 (32-bit) and don’t plan to upgrade.

    1. Mary wrote on

      I allowed firefox to install and run studies, restarted Firefox, went to about:studies and there’s no hotfix, checked again hrs later and still no hotfix. I can’t even find “app.normandy.run_interval_seconds” in about:config.

  27. JQ wrote on

    Does it make any difference what country we live in? (I’m American but live in France.) Because in about:studies I have something called “hotfix-reset-xpi-verification-timestamp-1548973” that is finished–but still same problem. Studies is enabled however, so I’m assuming I just need to wait longer?

    1. JQ wrote on

      P.S. Yes, I restarted Firefox. Hell, I rebooted the whole machine.

      1. JQ wrote on

        P.S. Aaaaand … just refreshed about:studies and, uh, guess what? The “signing intermediate bug” showed up active now. So, uh … yeah. I’m basically talking to myself here while this awaits moderation.

        There are days, man. There are days….

  28. Peter wrote on

    Will the fix be available to Comodo Ice Dragon users?

  29. John wrote on

    Any luck for those of us still running older versions of Firefox (56) with legacy add-on’s?

    1. Pennie wrote on

      It is now 9:25 am PDT on May 4, and though I have “Studies” enabled in options, there is no study update entitled “hotfix-update-xpi-signing-intermediate-bug-1548973” listed in “about:studies”. I am still not able to run, install alternatives for nor update my extensions (which all worked without issue until this most recent update to Firefox, version 66.0.3).

      I have refreshed and restarted my browser. I have uninstalled and reinstalled Firefox, version 66.0.3 (64-bit). I have tried every “alternative” there is for my extensions (UBlock Origin, Privacy Badger, Malwarebytes Browser Extension and Duck Duck Go Privacy Essentials), but just keep getting the “Download failed. Please check your connection” message (my connection is fine). I don’t want to have to download and install the developer or Nightly version of Firefox to override the signing requirement.

      It seems as though there has been enough time for a “Studies” hotfix to have been implemented. For some reason, though, it is not working for me…it is not even showing up. I don’t think I really have to tell you how frustrating this is. There is a reason I switched to Firefox; now, unfortunately, it looks like I might have to switch to a different browser (yes, those extensions – and my privacy – are that important to me, as they are to so many others).

  30. DegenerateBeast wrote on

    I removed the distribution folder containing my custom “policies.json” and was then able to revert the necessary about:config changes…I THINK. Studies are enabled within the preferences menu and the option seems to be sticking but I’m not sure that I set the “app.normandy.api_url” correctly back to default:

    …^^ is that the correct URL to allow studies and are there any other about:config values that I should check? I already reverted:

    *.normandy.enabled TRUE
    *.normandy.firstrun TRUE
    *.normandy.remotesettings.enabled FALSE
    *.shield.optoutstudies.enabled TRUE

    …I’m working with a heavily modified configuration via user.js and “freeballing” without it (even temp) is not an option for me. I also cannot/will not work with a FF fork, Gaggle Chrome or one of the myriad Chrome offshoots.

    “Help me Mozilla Firefox, you’re my only hope”.

    1. DegenerateBeast wrote on


      I used the “normandy.interval_run_seconds to 5” trick (thanks, David), restarted, verified that the requisite study has been applied and is active….but still no luck with my battery of crucial extensions.

      Those of us who have spent hours under the proverbial hood shouldn’t have to go back and hunt down user.js config changes that we enacted for privacy/security reasons in order to apply this “fix”. I’m losing Bitcoin by the minute here…

  31. Roberto Venturi wrote on

    I have hotfix-reset-xpi-verification-timestamp-1548973 active
    the other hotfix-update-xpi-signing-intermediate-bug-1548973 is not present

    Also i have prefflip-push-performance-1491171 active

    Firefox x64 66.0.3 on windows7

    Still waiting for a fix

  32. Ano wrote on

    I love Firefox but thats just inacceptable

  33. Hans wrote on

    I put a checkmark at
    “Firefox das Installieren und Durchführen von Studien erlauben”
    to allow studies, however, after I close the “Einstellungen” window and open it again, the checkmark has disappeared. Re-starting Firefox (FF 66.03, WIN 10) does not help.

    The latest study shown in “about:studies” is “pref-flip-screenshots-release-1369150•Abgeschlossen”

    What to do now?

    1. Luther wrote on

      I have the same issue.

    2. Vogelwild wrote on

      Same here, the option resets itself and the checkmark disappears, even restarting FF doesn’t help. My about:studies is completely empty, white. Not going to create a new FF profile just for this to work, so I’ve set xpinstall.signatures.required to false in about:config and that pretty much solved the whole issue. All add-ons running as expected.

  34. Jayson wrote on

    still not seeing any changes. How long can it take to show up in active studies?

  35. Shane Matthews wrote on

    ETA on this, and why isn’t there just a manual update option for studies?

    Using FF56 so yeah would be nice if you gave me back my addons thanks

    1. Maks wrote on

      I’m also using FF56 and i agree with Shan completely. This temp solution of the add-on problem is completely unacceptable (as the the add-on problem itself is in the first place). I use FireFox 56 with the old add-ons or no FF at all.

  36. Namari wrote on

    Firefox 48. MacOS. I don’t even have this enable studies option anywhere. About;studies page doesn’t seem to exist for my version: The address isn’t valid
    Is there going to be a fix for us, old version users?

    1. Ebby wrote on

      Another old version user, entirely content with my old Firefox (56.0.2), tweaked and tuned to run the way I wanted, in my old OS, on my old Mac. Until someone ‘out there’ tried to fix what ‘ain’t broke’ for me.

      I finally stumbled across this blog; it might have been helpful to add the Bug Notice and link to the Add-ons Page on the Firefox site. With many add-ons showing Warning Notices in my browser, I’ve removed things I depended on, and cannot download replacements.

      Can anyone confirm this six-hour fix puts things back to normal for all Firefoxes? Frankly, I’d rather go to a site and trust my own downloads that wait for yet another midnight skulk to ‘fix’ my machine behind my back.

    2. Harvey wrote on

      Disable signature enforcement – Enter about:config in your menu bar and click enter. Be careful to change nothing as you navigate down to find xpinstall.signatures.required and set it to false. This stops your browser confirming the validitity of the certificates for your extensions. This does create a minor security risk but it really shouldn’t matter. Then keep an eye on Mozilla’s homepage alerts to find out when the patch has been applied worlwide (including the legacy version fix) and go back and reset it to true.

  37. Lynda wrote on

    Showing “hotfix-reset-xpi-verification-timestamp-1548973•Complete” under Completed Studies.

    Under Active Studies, the only thing showing is “prefflip-push-performance-1491171•Active”.

  38. User wrote on

    Thank you guys, I know that it is the most difficult time, but I still believe that open and free is better than closed and controlled. I will be with you, thank you Firefox and thank you this open source community.


  39. Greg wrote on

    Very frustrating. Now all of my add-ons have disappeared and it won’t let me re-add them!

  40. JC wrote on

    Firefox 66.0.3 (64bit) and it worked.Thanks!

  41. Isaac Ambrosio wrote on

    Hello, currently I’m using an old version of Firefox, 51.0 spanish settings, on Windows 10. What are the steps to solve this issue?. Updating is NOT an option to me, due newer versions of Firefox does not support Java Applets or Servlets and Java enviroment (JRE) is indispensable to me and it runs better on Firefox than other shitty browsers.

    That option named “studies” is not included in this version.

    What can I do?. thanks.

    1. Sinan wrote on

      Isaac, they stated on a different thread that they don’t support old versions of ff.

  42. Klausi wrote on

    In FF61 there is NO “studies” option and the fix where you can download manually did not working for FF61 🙁 PLEASE FIX ALL VERSIONS.

  43. LivinFreerider wrote on

    Everything works again.

    Version 66.0.3

  44. VulcanTourist wrote on

    I have a worrisome potential barrier to receiving this bugfix: when I access about:studies, it results in a completely blank page!

  45. Koyemanaung(YoYo) wrote on

    Support and support device protect secure issues for my account and privacy.

  46. SuzyQ wrote on

    Been using esr for years now due to all the awful (& yes, drastic) changes ff continues to force on us that don’t allow us the freedom of customizing browser for ease of use AND rendered necessary add-ons unusable. Went thru everything in preferences. No studies to be found. add-ons STILL DISABLED. :-((

  47. Sephiros wrote on

    i’m using an old version of firefox, without studies option. Any way to fix problem for me?

  48. Dixie wrote on

    about:studies show only completed studies — none active. I am using 66.0.3 (64 bit). I have the ‘allow and run studies’ block checked. Will it take another 3 hours for the pertinent studies to show up and then another 6 hours for them to be active?

    1. Dixie wrote on

      Never mind!! It just worked!! Thank you SO MUCH!!!!!!!!

  49. Gérardn PERERA wrote on

    Hello guys,

    Seems to work also for me (version 66.0.3 (64 bits)) !

    Thanks a lot.

    Keep it up !

  50. aaa wrote on

    Immediately redirect to the post. This information shuld be known by all firefox users.

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