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How to Fix a Browser Hijack on Mozilla Firefox

Authored by:
Support.com Tech Pro Team
This Guided Path® was written and reviewed by Support.com’s Tech Pro team. With decades of experience, our Tech Pros are passionate about making technology work for you. We love feedback! Let us know what you think about this Guided Path® by rating it at the end.
Browser hijacking or 'pop-up phishing' involves fraudulent messages that unexpectedly pop up for users when they are surfing the web. In many cases, cyber criminals infect otherwise legitimate websites with malicious code that causes these messages to appear when people visit them.
The content of these messages themselves is what makes them so effective. Often, they present the unsuspecting website visitor with some kind of fraudulent warning from a well-known reputable company, typically about the security of their computer. Then they either prompt the visitor to download some tool to fix the problem, such as an antivirus application which turns out to be malware itself, or to call a fraudulent phone number for "support." The abnormal behavior of the message itself and the inability to close or navigate away from them, makes the fraudulent messages appear to be somewhat credible.
This guide will demonstrate how to rid yourself of the worrisome pop-up message, and then perform some simple operations to get Mozilla Firefox back to normal.
Hijacked firefox

But isn't this just a Pop-Up?

This guide focuses on hijacked browsers. While Pop-ups can be part of a hijacked browser, it takes a bit more work to clean a hijacked browser than a pop-up. Pop-ups are another beast entirely and covered in another guide.

Preventing Pop-Ups in Firefox

Select your computer's Operating System

This guide provides troubleshooting support for Windows and macOS. Select your operating system to proceed.

Windows
Windows runs on computers produced by multiple companies, such as Lenovo, Asus, Dell, Toshiba, Hewlett Packard, Acer, and Sony.Windows 10
macOS
Apple is the only company that makes macOS computers.macOS Mojave

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Browser hijacking or 'pop-up phishing' involves fraudulent messages that unexpectedly pop up for users when they are surfing the web. In many cases, cyber criminals infect otherwise legitimate websites with malicious code that causes these messages to appear when people visit them.
The content of these messages themselves is what makes them so effective. Often, they present the unsuspecting website visitor with some kind of fraudulent warning from a well-known reputable company, typically about the security of their computer. Then they either prompt the visitor to download some tool to fix the problem, such as an antivirus application which turns out to be malware itself, or to call a fraudulent phone number for "support." The abnormal behavior of the message itself and the inability to close or navigate away from them, makes the fraudulent messages appear to be somewhat credible.
This guide will demonstrate how to rid yourself of the worrisome pop-up message, and then perform some simple operations to get Mozilla Firefox back to normal.
Hijacked firefox

But isn't this just a Pop-Up?

This guide focuses on hijacked browsers. While Pop-ups can be part of a hijacked browser, it takes a bit more work to clean a hijacked browser than a pop-up. Pop-ups are another beast entirely and covered in another guide.

Preventing Pop-Ups in Firefox

Select your computer's Operating System

This guide provides troubleshooting support for Windows and macOS. Select your operating system to proceed.

Windows
Windows runs on computers produced by multiple companies, such as Lenovo, Asus, Dell, Toshiba, Hewlett Packard, Acer, and Sony.Windows 10
macOS
Apple is the only company that makes macOS computers.macOS Mojave

With a noisy, annoying, or even impossible to close pop up on Firefox you're going to need to force the application to quit before you can move on.

The following steps can be used to terminate any browser, but the examples below will demonstrate using Internet Explorer.
  1. Open the Windows Task Manager.
    Using the Taskbar
    • Using your right mouse button, right-click on your Taskbar. Then select Task Manager from the menu.
      Mouse with Right Mouse Button highlighted.
      Taskbar right-click menu with Task Manager highlighted.
    Using a Keyboard Shortcut
    • On your keyboard use Ctrl+Shift+Esc.
      Keyboard with Ctrl Shift and Esc highlighted
    Using the Lock Screen
    • You can do Ctrl+Alt+Del on your keyboard, then click on Task Manager.
      PC Desktop Keyboard with Ctrl-Alt-Del highlighted.
      GINA Screen with Task Manager highlighted.
  2. Select your browser, then select End Task.
    If the Task Manager is in Basic View
    Task Manager basic view with browser and End Task highlighted.
    If the Task Manager is in Advanced View
    Task Manager advanced view with browser and End Task highlighted.
When you next open your browser, if you are asked to restore a session / pages, select No, or close the message.

The first order of business is making sure that your browser is not holding onto some outdated or bad data in the form of an old cookie, cached version of the website it may be trying to load, etc. Clearing this data allows your browser to load the websites you're asking it to load freshly as if it had never been there before.

If there's a browser hijack saved in the cache, you'll clear it by doing this.

  1. Open Firefox, and select the Menu in the top-right corner.
    Mozilla Firefox
    Firefox browser with Menu highlighted
  2. Click on Options.
    Options highlighted
  3. Click on Privacy & Security.
    Privacy & Security highlighted
  4. Click the Clear History button located unther the History category.
    Clear History button highlighted
  5. Select the time range you wish to clear.
    Time range highlighted
  6. Click the Details button to expand them.
    Details expand button highlighted
  7. Choose the item categories you wish to clear.
    Item categories highlighted
    Setting Checkbox
    Browsing & Download History Checked

    Browsing History - While you browse Your browser will keep track of every page you visit, to try to make it easier to return. This can become corrupt due to modern active web pages.

    Download History - These are a list of files you've downloaded recently. It is entirely safe to delete, or keep this list, as it won't affect pages. Checking this option does not delete the files you've downloaded, just the list the browser keeps.

    Form & Search History Checked
    Information from entering forms online, such as your name, address, or other filled in information. This does not affect how a page loads, and can slow you down on your most commonly used pages.
    Cookies Checked
    Cookies are how websites 'know' you when you visit them multiple times. This file can become corrupt, and simply downloading a new one can fix many problems.
    You will have to log back into any pages you use, such as mail or social media.
    Active Logins Checked
    Active logins are sites that you are currently logged into that you have asked to remember that you are logged into. Clearing them just logs you out of these sites.
    Offline Website Data Unchecked
    If you've allowed it, a website can store files on your computer so that you can continue to use it when you are not connected to the Internet.
    Site Preferences Unchecked
    Site specific preferences, including the saved zoom level for sites, character encoding, and the permissions for sites.
     
  8. Click the Clear Now button.
    Clear Now button highlighted

Test Firefox for Continued Issues

  1. Open your browser and take note if it shows your normal home page or search page.
    Mozilla Firefox.
  2. Test your ability to search the web like you normally would and make sure there are no strange popups.
  3. If you're still having issues you may need to remove extensions.
Some browser extensions and addons can cause your browser to behave abnormally. They can cause your home page to navigate elsewhere, or even through popups. Removing any unwanted, unnecessary, or unused browser extensions and addons can get your web browser running properly again.
  1. Open Firefox and click on the three lines in the upper right hand corner.
    Mozilla Firefox
    Firefox with 3 lines highlighted. Screenshot
  2. Click on Add-ons.
    Firefox menu with addons highlighted. Screenshot
  3. Click on Extensions on the left.
  4. The following steps can be repeated to remove multiple browser extensions.
    • Then click on Remove for the extension you want to remove. If you don't remember installing the extension, using it, or know it its bad its a good practice to remove it.
      Extensions menu with Remove highlighted. Screenshot
      • If you accidentally removed something, click on Undo.
        Undo highlighted. Screenshot
    • You might get a new tab pop up upon removal, close the tab by hitting the X.
      Survey windows. Screenshot
      Browser Tab with X highlighted. Screenshot
  5. Extensions are now gone, you may have to restart your browser for it to take effect. If you removed a malicious extension, it might have changed your homepage.
If your browsing experience hasn't returned to normal, the next step is to verify that all Firefox settings are where they should be in order to provide you with the search experience you're familiar with. If any settings were previously 'hijacked' by a malicious extension and were not reverted back to what they were originally set to, your experience may still not be right.
  1. Open Firefox.
    Mozilla Firefox
  2. Enter about:plugins into address bar and hit enter, then review your plug-ins and remove any that are malicious.
    Firefox plugins
  3. Enter about:addons into the address bar and hit enter, then click Extensions.
    Firefox extensions
  4. Review your extensions and determine if any are malicious. Remove those that are.
  5. Click the Menu button in the top right of the screen.
    Firefox browser with Menu highlighted
  6. Click Options.
    Firefox menu showing options selected
  7. Click Home. If you have a custom URL set verify it is not malicious.
    Firefox homepage settings
  8. Click the Start Menu.
    Windows 10 Start Menu.
  9. Search for Firefox and right-click the result.
  10. Select Open File Location
    Firefox right click menu within windows 10
  11. Right-click the Firefox shortcut and select Properties.
    Firefox right click menu
  12. Click the Shortcut tab and verify that the Target only contains the path "C:\Program Files (x86)\Mozilla Firefox\firefox.exe" with nothing after it. Click OK when done.
    Firefox shortcut properties
  13. Open Firefox and verify your homepage is correct.

Test Firefox for Continued Issues

  1. Open your browser and take note if it shows your normal home page or search page.
    Mozilla Firefox
  2. Test your ability to search the web like you normally would and make sure there are no strange popups.
  3. If you're still having issues you may have a PUP.

Potentially unwanted programs, or "PUPs", often arrive bundled with your computer or can tag along with another software program you meant to install. Most times, they are snuck into the EULA as a "Recommended Offer" that many of us are so accustomed to just click right through. Lots of these types of programs end up being junkware that your computer will not benefit from. Unfortunately, some of these programs can add unwanted browser toolbars or extensions that can clutter your browser, track your web browsing, show additional advertisements, or change your search page and other related settings. Usually, unless these types of programs are removed, they will continue causing issues with your web browsing experience.

Example of a PUP installing a search bar

Remove PUPs via Windows 10 Settings
  1. Click Start (1), then click Settings (2).
    Windows start menu with the start button and settings highlighted.
  2. Next, Select Apps.
    Windows Settings with Apps highlighted.
  3. Scroll down and locate the app you wish to remove, and click on Uninstall.
    Apps screen with the uninstall option for an app highlighted.
  4. Carefully read any prompts in case there are special instructions. Proceed until the application is removed.
  5. Some applications may require that you reboot.
Remove PUPs via the Control Panel
  1. On your keyboard push and release the Windows Key and R at the same time.
    PC Desktop Keyboard with Windows key and R highlighted.
  2. You will see a Run window open up. Type in appwiz.cpl then click on OK.
    Run windows with appwiz.cpl typed and OK highlighted. Screenshot
  3. Locate a program you wish to remove within the list, click once on it to highlight it, then click on Uninstall.
    Uninstall window with program and uninstall highlighted. Screenshot
  4. Carefully read any prompts in case there are special instructions. Proceed until the application is removed.
  5. Some applications may require that your computer be restarted to complete the uninstallation.

Test your browser after removing any PUPs from your machine. This may require you to restart your browser or your computer beforehand depending on what was removed.

Unfortunately, your browser issue cannot be resolved via basic troubleshooting steps. Your machine will require hands-on service to determine the root cause of your issues.

With a noisy, annoying, or even impossible to close pop up on Firefox you're going to need to force the application to quit before you can move on.

  1. Select the Apple menu, then Force Quit.
    Apple menu with Force Quit highlighted.
  2. Highlight Firefox in the list, and select Force Quit.
    Force Quit with Firefox and Force Quit highlighted.
  3. You'll be prompted if you're sure, select Force Quit.
    Force quit prompt with Force Quit button highlighted.

Your web browser's homepage settings dictate the websites that are loaded when it is opened up. As integral as these settings are to your browsing experience they can be hijacked by malicious code and made to disrupt your online experience.

Let's check your settings and make sure they're okay.

  1. Open Firefox and click on the three lines in the upper right hand corner.
    Mozilla Firefox
    Firefox with 3 lines highlighted. Screenshot
  2. Click on Preferences.
    Firefox menu with Preferences highlighted. Screenshot
  3. Click on Home. If there is a custom URL you do not want, you can change it. If there's a URL here you don't recognize you should change it.
    Firefox Settings menu with Home and Custom URL highlighted. Screenshot
  4. If after performing the change, you notice no difference and the website is still appearing you'll need to get rid of an extension.
Some browser extensions and addons can cause your browser to behave abnormally. They can cause your home page to navigate elsewhere, or even through popups. Removing any unwanted, unnecessary, or unused browser extensions and addons can get your web browser running properly again.
  1. Open Firefox and click on the three lines in the upper right hand corner.
    Mozilla Firefox
    Firefox with 3 lines highlighted. Screenshot
  2. Click on Add-ons.
    Firefox menu with addons highlighted. Screenshot
  3. Click on Extensions on the left.
  4. The following steps can be repeated to remove multiple browser extensions.
    • Then click on Remove for the extension you want to remove. If you don't remember installing the extension, using it, or know it its bad its a good practice to remove it.
      Extensions menu with Remove highlighted. Screenshot
      • If you accidentally removed something, click on Undo.
        Undo highlighted. Screenshot
    • You might get a new tab pop up upon removal, close the tab by hitting the X.
      Survey windows. Screenshot
      Browser Tab with X highlighted. Screenshot
  5. Extensions are now gone, you may have to restart your browser for it to take effect. If you removed a malicious extension, it might have changed your homepage.

We want to make sure that your browser is not holding onto some outdated or bad data in the form of an old cookie, cached version of the website it may be trying to load, etc. Clearing this data allows your browser to load the websites you're asking it to load freshly as if it had never been there before.

  1. Open Firefox, and select the Menu in the top-right corner.
    Mozilla Firefox
    Firefox browser with Menu highlighted
  2. Click on Options.
    Options highlighted
  3. Click on Privacy & Security.
    Privacy & Security highlighted
  4. Click the Clear History button located unther the History category.
    Clear History button highlighted
  5. Select the time range you wish to clear.
    Time range highlighted
  6. Click the Details button to expand them.
    Details expand button highlighted
  7. Choose the item categories you wish to clear.
    Item categories highlighted
    Setting Checkbox
    Browsing & Download History Checked

    Browsing History - While you browse Your browser will keep track of every page you visit, to try to make it easier to return. This can become corrupt due to modern active web pages.

    Download History - These are a list of files you've downloaded recently. It is entirely safe to delete, or keep this list, as it won't affect pages. Checking this option does not delete the files you've downloaded, just the list the browser keeps.

    Form & Search History Checked
    Information from entering forms online, such as your name, address, or other filled in information. This does not affect how a page loads, and can slow you down on your most commonly used pages.
    Cookies Checked
    Cookies are how websites 'know' you when you visit them multiple times. This file can become corrupt, and simply downloading a new one can fix many problems.
    You will have to log back into any pages you use, such as mail or social media.
    Active Logins Checked
    Active logins are sites that you are currently logged into that you have asked to remember that you are logged into. Clearing them just logs you out of these sites.
    Offline Website Data Unchecked
    If you've allowed it, a website can store files on your computer so that you can continue to use it when you are not connected to the Internet.
    Site Preferences Unchecked
    Site specific preferences, including the saved zoom level for sites, character encoding, and the permissions for sites.
     
  8. Click the Clear Now button.
    Clear Now button highlighted

Test Firefox for Continued Issues

  1. Open your browser and take note if it shows your normal home page or search page.
    Mozilla Firefox
  2. Test your ability to search the web like you normally would and make sure there are no strange popups.
  3. If you're still having issues you may have a PUP.

Potentially unwanted programs, or "PUPs", often arrive bundled with your computer or can tag along with another software program you meant to install. Most times, they are snuck into the EULA as a "Recommended Offer" that many of us are so accustomed to just click right through. Lots of these types of programs end up being junkware that your computer will not benefit from. Unfortunately, some of these programs can add unwanted browser toolbars or extensions that can clutter your browser, track your web browsing, show additional advertisements, or change your search page and other related settings. Usually, unless these types of programs are removed, they will continue causing issues with your web browsing experience.

Example of a PUP installing a search bar

Remove PUPs on macOS

  1. Open the Finder from the dock.
    Finder highlighted on the dock
  2. Click on Applications on the left.
    Application highlighted
  3. Drag the app you wish to remove to the trash can.
    Drag app to the trashcan
  4. Right click on the trashcan and click Empty Trash.
    Empty Trash highlighted

Test your browser after removing any PUPs from your machine. This may require you to restart your browser or your computer beforehand depending on what was removed.

Unfortunately, your browser issue cannot be resolved via basic troubleshooting steps. Your machine will require hands-on service to determine the root cause of your issues.