Avast/AVG users are getting an alert about their prefs.js file, which stores important custom settings for Mozilla software. If you use Avast/AVG, the file may have been quarantined in the past few hours. Does that sound like a possibility for you?

It's not yet clear exactly what is triggering the detection, so it's a bit soon to sound an all clear to restore that file from quarantine (if that is an option). Hopefully we'll know more soon.

That is exactly what happened. Immediately did scan, it is scanning now. So pref file has been quar. Do I need to contact aVAST support?

Avast forums now say it was a false positive and they've issued a fix --

• https://forum.avast.com/index.php?topic=318639.msg1683272#msg1683272
• https://forum.avast.com/index.php?topic=318640.msg1683270#msg1683270

-- but unfortunately, we still have to clean up the damage by restoring the file to its original location.

Does Avast have a feature for this in its quarantine?

The original path on disk would have been listed in an alert. If Avast shows historical alerts, and you can get the file back , then you could drop it back in that folder (and replace the new one without any useful information in it that most likely was created there the next time you started Thunderbird).

Can anybody help me find my pref file. Was on phone with AVAST for over an hour, they gave up and told me to call TB. I can't find my pref file that was quar by AVast. If did find it I don't know where to put it to make it work again. I had this problem a few years ago and was always able to fix it but can't seem to find it now. can anybody help? John

Hi John, I'm not sure whether Avast gave up on finding the file in the quarantine, or gave up on restoring the file.

If you have the file in the quarantine, great. We can work with that.

If you do not have the file:

Let's check for a backup. This backup may not have all the proper settings in your latest file but it probably would be better than nothing.

First, set Windows to show all hidden files and folders. See: https://support.microsoft.com/en-us/windows/show-hidden-files-0320fe58-0117-fd59-6851-9b7f9840fdb2

Next, navigate to your current prefs.js file. I think it would be here:

C:\Users\<username>\AppData\Roaming\Thunderbird\Profiles\<randomly.named\ </p>

Right-click the prefs.js file (or prefs, if your Windows hides common file extensions) and open Properties.

Does your Properties dialog have a Previous Versions tab? If so, click that and Windows should search its restore points for the last backup it created.

Anything there to try?

You can export or copy (I can't recall the exact wording) the backup prefs.js file to your Windows desktop for easier access, and then later try switching that into your profile folder in place of the useless file created after your good one was quarantined. (Thunderbird needs to be closed during the switch.)

Thank you for your help. This is a real mess. I had the quarantined file and restored it with exception and that at lease let me open thunderbird. There were actually two quarantined prefs files but one will not restore. I tried one previous version I found just by doing a complete computer search for prefs files and found one which was in Jan22 and I put it in and it gives a message that my preferences file is missing or corrupted. I am now afraid that the avast support guy messed up the file I really needed somehow. When this has happened to me in years past I have always been able to fix it within minutes but not this time. I will keep looking around and thinking about it. I also have a Thunderbird file folder somewhere in a moving box and if I can find that I have some great instructions in there too. Thanks again for your help. If you think of anything else let me know.

Hmm, another prefs.js from elsewhere on your computer might have been from a Firefox profile? That one definitely wouldn't work for Thunderbird, so maybe that was why it was considered corrupted. Hope you are able to find a backup.

Restore files from Avast quarantine:

https://www.reddit.com/r/avast/comments/tkabes/avast_quarantined_thunderbird_emails_prefsjs_file/

I restored the prefs,js but my emails are all missing! Not sure what to do from here. UGH!