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  • Active
  • Severity: High
  • Malware
  • Windows, Mac
  • Verified · Dec 2017

How to remove Mozilla Firefox Critical ERROR

A step-by-step removal guide for affected devices. Follow the verified procedure below — most readers complete it in under 10 minutes.

Olivia Morelli · Ransomware analyst

Mozilla Firefox Critical ERROR is not legitimate security alert

Screenshot of Mozilla Firefox Critical ERROR

Mozilla Firefox Critical ERROR is a fake message sent by cyber criminals to trick computer user’s that their personal and banking information is at risk. However, it’s a scam that is similar to Microsoft Edge Critical error or Internet Explorer Critical error. The major differences are that scammers target different browser’s users [1]and use different phone number to communicate with victims.

Users are usually redirected to Mozilla Firefox Critical ERROR scam website after adware infiltration or visit the infected site. In the background, it is written that someone tried to get access to personal logins and bank information. Additionally, it warns about the possibility of damaged hard disk data due to the trojan virus attack.

Additionally, Mozilla Firefox Critical ERROR virus delivers a pop-up that requires authentication. People are asked to enter their username and password. Obviously, no one has them. So, they are asked to call a “toll-free” support number. The full message of the fake alert:

http://0x00381136100.bid is requesting your username and password. The site says:
“FIREFOX_CRITICAL_ERROR_0xKB1546764_CALL_HELP_DESK: +1 (877) 556-6888 (Toll-Free)”

However, there are several variations of the Mozilla Firefox Critical ERROR scam which provides other phone numbers and error codes. Another version was reported giving a 0xKB6301092 error and using +1 (877) 777-8951 phone number, but that might not be it.

Keep in mind that calling provided number is not recommended. Fake tech support specialists might try to obtain sensitive information, swindle the money,[2] or sell useless software that might be malicious too. Additionally, they might convince you to install remote access tools and get control over your computer.

If you ended up on a scam website only once, you might not need to take any additional actions. It should be enough to close Firefox and forget about the accident. However, some users report that they were unable to close it. In this case, you should force quit the browser in order to remove Mozilla Firefox Critical ERROR from the screen.

However, if you are frequently redirected to this tech support scam site, you might have adware program installed. You can suspect infiltration of the ad-supported app if you:

  • noticed an increased amount of pop-ups, banners, and other types of online ads;
  • found random text turned into hyperlinks;
  • are continuously redirected to other suspicious websites.

In this case, we highly recommend opting for the automatic Mozilla Firefox Critical ERROR removal. It requires scanning the system with reputable anti-malware software, such as FortectIntego.

Image of Mozilla Firefox Critical ERROR scam

Reason to be careful with freeware and shareware downloads

Mozilla Firefox Critical ERROR adware, as well as many other potentially unwanted programs (PUPs), often spread bundled with free programs, including freeware and shareware. Incorrect installation of a new application might lead to the hijacked web browser. Thus, you might suffer from redirects, aggressive ads, and other suspicious activities.

For this reason, users should attentively and correctly install programs in order to make sure that they do not let any suspicious components get inside the system as well. A security team from DieViren[3] suggests following these tips:

  • Use official software download sites instead of unauthorized and unknown services;
  • Read EULA, Terms of Use, Privacy Policy and other provided information by developers;
  • Use Advanced/Custom settings rather than Quick/Recommended;
  • Opt out pre-selected apps that are offered to download along with the program you need.

Get rid of “Mozilla Firefox Critical ERROR” pop-ups

To stop redirects to suspicious websites, you have to remove Mozilla Firefox Critical ERROR adware from the computer. You can follow the manual guide below and try to locate adware-related components manually. However, it might be challenging, and unwanted browsing activities might continue.

To succeed, we recommend going for automatic Mozilla Firefox Critical ERROR removal. After the system scan with an updated anti-malware software, you will need to reset Mozilla Firefox and continue browsing the web without any problems.

Uninstall from Windows

Uninstall from Windows 10/8:

  1. Type Control Panel into the Windows search box and open the result.
  2. Under Programs, select Uninstall a program.Uninstall from Windows 10/8

Uninstall from Windows 7/XP:

  1. Click on Windows Start > Control Panel (Windows XP users should click on Add/Remove Programs).
  2. In Control Panel, select Programs > Uninstall a program.Uninstall from Windows 7/XP

Remove the unwanted program:

  1. In the Programs and Features window, look for any recently installed suspicious entries, select them, and click Uninstall.
  2. If User Account Control appears, click Yes to confirm, then complete the removal.Uninstall the unwanted program from Windows

Delete from macOS

Remove the unwanted application:

  1. From the menu bar, select Go > Applications.
  2. In the Applications folder, look for any suspicious entries, then drag them to Trash (or right-click and pick Move to Trash).Uninstall from Mac

Delete leftover files and folders:

  1. Select Go > Go to Folder.
  2. Enter /Library/Application Support and remove any suspicious folders related to the unwanted program.
  3. Repeat the same check in the /Library/LaunchAgents and /Library/LaunchDaemons folders, deleting any suspicious entries.Delete leftover files from Mac
  4. Finally, empty the Trash to permanently remove the leftovers.

Reset Internet Explorer

Remove dangerous add-ons:

  1. Open Internet Explorer, click on the Gear icon (IE menu) on the top-right corner of the browser
  2. Pick Manage Add-ons.
  3. You will see a Manage Add-ons window. Here, look for suspicious plugins. Click on these entries and select Disable.Remove add-ons from Internet Explorer

Change your homepage if it was altered:

  1. Open IE and click on the Gear icon.
  2. Select Internet Options.
  3. In the General tab, delete the Home page address and replace it by your preferred one (for example, Google.com).
  4. Click Apply and then select OK.Reset IE homepage

Delete temporary files:

  1. Press on the Gear icon and select Internet Options.
  2. Under Browsing history, click Delete...
  3. Select relevant fields and press Delete.Clear temporary files from Internet Explorer

Reset Internet Explorer:

  1. Click on Gear icon > Internet options and select Advanced tab.
  2. Select Reset.
  3. In the new window, check Delete personal settings and select Reset.Reset Internet Explorer

Remove from Microsoft Edge

Delete unwanted extensions from MS Edge:

  1. Select Menu (three horizontal dots at the top-right of the browser window) and pick Extensions.
  2. From the list, pick the extension and click on the Gear icon.
  3. Click Remove.Remove extensions from Edge

Clear cookies and other browser data:

  1. Click on the Menu (three horizontal dots at the top-right of the browser window) and select Settings > Privacy, search, and services..
  2. Under Clear browsing data, pick Choose what to clear.
  3. Select Cookies and other site data and Cached images and files. (apart from passwords, although you might want to include Media licenses as well, if applicable) and click on Clear.Clear Edge browsing data

Restore new tab and homepage settings:

  1. Click the menu icon and choose Settings.
  2. Then find On startup section.
  3. Click Remove next to any suspicious startup page.

Reset MS Edge if the above steps did not work:

  1. Press on Ctrl + Shift + Esc to open Task Manager.
  2. Click on More details arrow at the bottom of the window.
  3. Select Details tab.
  4. Now scroll down and locate every entry with Microsoft Edge name in it. Right-click on each of them and select End Task to stop MS Edge from running.Reset MS Edge

Instructions for Chromium-based Edge

Delete extensions from MS Edge (Chromium):

  1. Open Edge and click select Settings > Extensions.
  2. Delete unwanted extensions by clicking Remove.Remove extensions from Chromium Edge

Clear cache and site data:

  1. Click on Menu and go to Settings.
  2. Select Privacy, search and services.
  3. Under Clear browsing data, pick Choose what to clear.
  4. Under Time range, pick All time.
  5. Select Clear now.Clear browser data from Chroum Edge

Reset Chromium-based MS Edge:

  1. Click on Menu and select Settings.
  2. On the left side, pick Reset settings.
  3. Select Restore settings to their default values.
  4. Confirm with Reset.
  5. This will disable extensions and reset startup pages but will not delete bookmarks, saved passwords, or browsing history.Reset Chromium Edge

Remove from Mozilla Firefox (FF)

Remove dangerous extensions:

  1. Open Mozilla Firefox browser and click on the Menu (three horizontal lines at the top-right of the window).
  2. Select Add-ons.
  3. In here, select the unwanted extension and click Remove.Remove extensions from Firefox

Reset the homepage:

  1. Click three horizontal lines at the top right corner to open the menu.
  2. Choose Settings.
  3. Under Home, set your preferred homepage and new tab settings.

Clear cookies and site data:

  1. Click Menu and pick Settings.
  2. Go to Privacy & Security section.
  3. Scroll down to locate Cookies and Site Data.
  4. Click on Clear Data...
  5. Select Cookies and Site Data and Temporary cached files and pages, then click Clear.Clear cookies and site data from Firefox

Reset Mozilla Firefox

If clearing the browser as explained above did not help, reset Mozilla Firefox:

  1. Open Mozilla Firefox browser and click the Menu.
  2. Go to Help and then choose Troubleshooting Information.Reset Firefox 1
  3. Under Give Firefox a tune up section, click on Refresh Firefox...
  4. Once the pop-up shows up, confirm the action by pressing on Refresh Firefox.Reset Firefox 2

Remove from Google Chrome

Delete malicious extensions from Google Chrome:

  1. Open Google Chrome, click on the Menu (three vertical dots at the top-right corner) and select More tools > Extensions.
  2. In the newly opened window, you will see all the installed extensions. Uninstall all suspicious extensions related to the unwanted program by clicking Remove.Remove extensions from Chrome

Clear cache and web data from Chrome:

  1. Click on Menu and pick Settings.
  2. Under Privacy and security, select Clear browsing data.
  3. Select Browsing history, Cookies and other site data, as well as Cached images and files.
  4. Click Clear data.Clear cache and web data from Chrome

Change your homepage:

  1. Click menu and choose Settings.
  2. Look for a suspicious site in the On startup section.
  3. Click on Open a specific or set of pages and click on three dots to find the Remove option.

Reset Google Chrome:

If the previous methods did not help you, reset Google Chrome to eliminate all the unwanted components:

  1. Click on Menu and select Settings.
  2. In the Settings, scroll down and click Advanced.
  3. Scroll down and locate Reset and clean up section.
  4. Now click Restore settings to their original defaults.
  5. Confirm with Reset settings.Reset Chrome 2

Delete from Safari

Remove dangerous extensions:

  1. Open Safari, click Safari in the menu at the top-left of the screen, and select Preferences.
  2. Go to the Extensions tab, look for any suspicious entries, and click Uninstall to remove them.Remove extensions from Safari

Clear history and website data:

  1. Click Safari in the menu and pick Clear History.
  2. Set Clear to all history and confirm with Clear History.Clear history from Safari

Reset Safari:

  1. Click Safari in the menu and select Preferences > Advanced.
  2. Enable Show Develop menu in menu bar.
  3. From the menu bar, click Develop and select Empty Caches.Reset Safari

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