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How can I avoid firefox resetting my browser preferences when my antivirus software scans my computer

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How can I avoid firefox resetting my browser preferences when my antivirus software scans my computer

Starting on 2/19/2013 each time my antivirus software scans my computer (Daily), various Firefox browser preferences are being reset. (It appears Firefox may be being reset to default.) My home page is being reset to mozilla etc...

I have reset Firefox, un-installed and re-installed Firefox to no avail. 
Each time the computer is scanned my browser preferences are lost.

The system info follows: Windows 7 pro 64 bit AVG antivirus 2013 current build.

Firefox v19.
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Legendary Contributor

Re: How can I avoid firefox resetting my browser preferences when my antivirus software scans my computer

I can't recall anyone else reporting that AVG was doing this. Actually, it would be helpful to know exactly what AVG is doing. Your home page is stored in a file named prefs.js in your personal Firefox settings folder (your Firefox profile folder). Is it deleting that file? Replacing it from a "clean" copy it keeps? Has it marked the file read-only so that your changes are not saved between sessions?

Could you make a backup copy of your profile folder so you have it around for comparison after the scan runs? You might need to store it on a USB flash drive so it doesn't get scanned, too.

To access that folder, you can use

Help > Troubleshooting Information > "Show Folder" button

Navigate up one level to Ctrl+drag the folder to the copy destination.

14 REPLIES
Legendary Contributor

Re: How can I avoid firefox resetting my browser preferences when my antivirus software scans my computer

I can't recall anyone else reporting that AVG was doing this. Actually, it would be helpful to know exactly what AVG is doing. Your home page is stored in a file named prefs.js in your personal Firefox settings folder (your Firefox profile folder). Is it deleting that file? Replacing it from a "clean" copy it keeps? Has it marked the file read-only so that your changes are not saved between sessions?

Could you make a backup copy of your profile folder so you have it around for comparison after the scan runs? You might need to store it on a USB flash drive so it doesn't get scanned, too.

To access that folder, you can use

Help > Troubleshooting Information > "Show Folder" button

Navigate up one level to Ctrl+drag the folder to the copy destination.

New Contributor

Re: How can I avoid firefox resetting my browser preferences when my antivirus software scans my computer

I followed directions to verify the prefs script file location. When I try to view the contents I get an error condition as follows;

                          line: 1
                          character: 1
                          Error:   Invalid Character
                          Code:   800A03F6
                          Source:  microsoft JScript Compilation Error

I am assuming the file should contain script detailing user preferences?

Legendary Contributor

Re: How can I avoid firefox resetting my browser preferences when my antivirus software scans my computer

Hi esmer, you got a little ahead of me.

The default action for a .js file is to execute it. Windows displays an "S" icon indicating that this is the default action. For your security, never, ever double-click such a file because you have no idea what it will do to your system. (I've written scripts to purge files and edit the Windows registry; some of them are serious programs.) Because the prefs.js file is designed to change settings within Firefox, thankfully it doesn't do any damage when you double-click it.

To view the contents of a script file, right-click it and choose Edit, which will open the file in Notepad. If the lines all run together, close Notepad, right-click, and try Open With and choose a more intelligent editor such as Wordpad.

Or, to compare two files, try WinMerge.

New Contributor

Re: How can I avoid firefox resetting my browser preferences when my antivirus software scans my computer

Thanks for the balance on raw enthusiasm!

Ok, I have tried the following;

I set up my preferences in firefox and verified them in prefs using notepad.

Specifically:

1: I chose my homepage and verified it had been changed in prefs...

      I then ran a full scan and verified the scan caused the homepage to be changed in prefs...

2: I again changed the homepage back to mine,

      I verified again it had been correctly changed in prefs, 
      I then did a firefox reset.

In both instances the change in prefs was to the build override homepage. it appears AVG's scan is causing a reset in Firefox?

Legendary Contributor

Re: How can I avoid firefox resetting my browser preferences when my antivirus software scans my computer

Firefox's built-in Reset feature moves your existing settings folder to the desktop and I don't think AVG would be able to trigger that. But the effect may be similar, just without creating the backup of your old settings.

There must be some way to stop this in AVG or these forums would light up with many posts describing the same problem.

New Contributor

Re: How can I avoid firefox resetting my browser preferences when my antivirus software scans my computer

one additional item...

I went to verify the contents of my local prefs file again using windows explorer and noticed some unusual behavior. if I click on the file once to select it it de-selects itself in about 3 seconds, typically before I can right click to edit. I verified I have "double click to open an item" selected in explorer I've never seen that behavior in windows explorer before.

New Contributor

Re: How can I avoid firefox resetting my browser preferences when my antivirus software scans my computer

I've got the exact same problem. Even got the same error message as esmer when viewing the prefs script. Seems to happen every morning after AVG runs my daily scan. I hate having to redo everything each morning (been happening for a couple of days now). I'd hate to have to stop using either programs.

New Contributor

Re: How can I avoid firefox resetting my browser preferences when my antivirus software scans my computer

First, I need to say Thanks! to jscher2000 for all your interest in the problem.

so we're aware, I have AVG examining this from their end as well.

additionally,

I believe this started occurring with the upgrade to Firefox v19. is there a way to determine the date of the last upgrade?

Legendary Contributor

Re: How can I avoid firefox resetting my browser preferences when my antivirus software scans my computer

I believe this started occurring with the upgrade to Firefox v19. is there a way to determine the date of the last upgrade?

Firefox 19 was just released on Tuesday, Feb. 19th. I'm not sure whether Firefox stores your exact update date/time somewhere.