Every time I start Firefox (60), it sends request to https://anti-captcha.com/ in background. it doesn't show anything but when I check in fiddler it loads HTML and JavaScripts. Usually I disable JavaScript.

I didn't install any extensions from this site.

I test Firefox in safe-mode, but it does it again. I search about:config page, but there isn't anything about this domain.

Where can I find register point of this site in my browser? How can I remove it?


I create new profile with firefox -p and start firefox with new profile. Then I come back to default user, it seems solved the problem.

  • 1
    Check your installed plugins. – DavidPostill Jun 24 '18 at 5:51
  • there isn't any new plugins or extensions. – mando Jun 24 '18 at 13:41
  • It may be an existing plugin - try starting Firefox in SAFE mode. – DrMoishe Pippik Jun 25 '18 at 0:31
  • I know every plugins that I have installed. I've tried Safe-Mode, but no luck. – mando Jun 25 '18 at 3:37

This may not be your case but I have seen hidden batch scripts in the "C:\Program Files\Mozilla Firefox" folder that redirect the users homepage by altering the user.js file in Firefox.

Change the Windows Folder Options in the Windows Control Panel to show hidden files and hidden system files.

Look in the "C:\Program Files\Mozilla Firefox" folder and if you see any batch scripts such as "firefox.bat" you need to delete them and also delete any Desktop shortcuts to Firefox as they have been corrupted to point at the fake "firefox.bat" script and create new Desktop shortcuts from the REAL firefox.exe found in the same "C:\Program Files\Mozilla Firefox" folder.

If there is a "firefox.bat" file in there most likely there will also be ones in the other browser folders as well such as Chrome and IE that need to be deleted and new Desktop shortcuts created as well.

You can also run the excellent browser cleaner called "ADWCleaner" from Malwarebytes to clean up any registry settings but ADWCleaner will NOT remove any hidden batch scripts. Those have to be removed manually as stated above.

  • Thanks for your response. there wasn't any bat file in firefox folder. I think that site registers something inside Firefox. when Firefox loaded (2-3 sec later) firefox sends some request . FF homepage seems OK. Chrome have no problem. – mando Jun 24 '18 at 13:32

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