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Homepage keeps resetting; User.js file was deleted

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  • Last reply by cor-el

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I got hit with a trojan horse recently and had to re-set Firefox. My user.js file was cleaned out by Adware, so now whenever I restart Firefox, it acts like it's never been started on my computer before. How can I create a new user.js file?

I got hit with a trojan horse recently and had to re-set Firefox. My user.js file was cleaned out by Adware, so now whenever I restart Firefox, it acts like it's never been started on my computer before. How can I create a new user.js file?

All Replies (6)

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You normally do not need a user.js in the profile folder.

Do you know what content was in the user.js file if you previously had such a file in the Firefox profile folder?

What kind of problems do you have?

Is Firefox still using the same default profile or does a new profile gets created?

The latter can be a problem with the profiles.ini file.

Otherwise there might be a problem with the prefs.js file if preferences aren't kept.


The user.js file is only present if you or other software has created this file and normally it wouldn't be there. You can check its content with a plain text editor (right-click: Open with) if you didn't create this file yourself.

The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.

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Firefox stores changes you make through the Options dialog, such as your home page, in prefs.js; it will look for a user.js file as a potential override, but does not store your changes there.

You could try copying the prefs.js file from your old profile folder (it's inside the "Old Firefox Data" folder the Reset created on your desktop) to your currently active Firefox profile. But it could contain traces of the infection that you had before...

If your settings keep getting lost each time you close and start Firefox again, you should address that first. Please consider:

  • Any software you may have that undoes browser settings changes, such as the "Surfing Protection" feature of Advanced SystemCare or the Home Page protection feature of some security software.
  • If you still have Search Protect in the Windows Control Panel, Uninstall a Program, make sure to remove that.
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Sorry, I wasn't clear enough. The old user.js file is already deleted; the new one is stuck in quarantine and I can't scrub it. So there basically is no file; it doesn't exist. The profile.ini is still there but says only this:

[General] StartWithLastProfile=1

[Profile0] Name=default IsRelative=1 Path=Profiles/ndu6u7l4.default

There is no fixing preferences or browser settings issues here; I've already tried all that. Without the user.js file it's going to act like FF has never been used on this system before.

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But in normal operation, there is no user.js file and Firefox works fine without it. The one in quarantine likely is in there because it was created or contaminated by unwanted software. My advice is to forget about user.js and consider the other information in this thread.

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It would appear my prefs.js file is quarantined as well; that may explain the problem better than the user.js. Fastest fix may be to uninstall/reinstall.

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Did you try to delete the prefs.js file to reset all prefs?

Delete a possible user.js file and numbered prefs-##.js files and rename (or delete) the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in the current Firefox release.