How to Fix Firefox Error sec_error_unknown_issuer?

Fix Firefox Error code sec_error_unknown_issuer:

Fix  Error sec_error_unknown_issuer with Online Tech Support Company focused on helping our customers avoid trouble due to Mozilla Firefox. Sometimes users using Mozilla Firefox to browse a website, you visit a website using an SSL certificate and receive an error that your connection is not secure. If you click to learn more, you see the following message below.

Fix Firefox error

  1. Repair Registry Entries Associated with Error sec_error_unknown_issuer.

Follow these steps to Repair Registry for Error sec_error__unknown_issuer:

  • Click the Start button.
  • Type “command” in the search box… DO NOT hit ENTER yet!
  • While holding CTRL-Shift on your keyboard, hit ENTER.
  • You will be prompted with a permission dialog box.
  • Click Yes.
  • A black box will open with a blinking cursor.
  • Type “regedit” and hit ENTER.
  • In the Registry Editor, select the Error sec_error_unknown_issuer-related key (eg. Firefox) you want to back up.
  • From the File menu, choose Export.
  • Follow the Save In the list, select the folder where you want to save the Firefox backup key.
  • In the File Name box, type a name for your backup file, such as “Firefox Backup”.
  • Export Range box, be sure that “Selected branch” is selected.
  • Click Save.
  • The file is then saved with a .reg file extension.
  • You now have a backup of your Firefox-related registry entry.
  1. Conduct a Full Malware Scan of Your PC:

  2. Clean Out Your System Junk (Temporary Files and Folders) With Disk Cleanup (cleanmgr)

Fix Firefox Error sec_error_unknown_issuer (solution)

How to run Disk Cleanup (cleanmgr) (Windows XP, Vista, 7, 8, and 10):

  • Click the Start button.
  • Type “command” in the search box… DO NOT hit ENTER yet!
  • While holding CTRL-Shift on your keyboard, hit ENTER.
  • You will be prompted with a permission dialog box.
  • Click Yes.
  • A black box will open with a blinking cursor.
  • Type “cleanmgr” and hit ENTER.
  • Disk Cleanup will begin calculating how much occupied disk space you can reclaim.
  • The Disk Cleanup dialog box will appear with series of checkboxes you can select. In most cases, the “Temporary Files” category will occupy the most disk space.
  • Check the boxes of the categories you want to clean and click OK.
  1. Update Your PC Device Drivers:
  2. Utilize Windows System Restore to “Undo” Recent System Changes

To use System Restore (Windows XP, Vista, 7, 8, and 10):

  • Click the Start button.
  • In the search box, type “System Restore” and hit ENTER.
  • In the results, click System Restore.
  • Enter any administrator passwords (if prompted).
  • Follow the steps in the Wizard to choose a restore point.
  • Restore your computer.
  1. Uninstall and Reinstall the Firefox Program Associated with Error sec_error_unknown_issuer.

Uninstall and Reinstall Instructions for Windows 8, 10:

  • Hover the cursor in the bottom left of the screen to produce the Start Menu image.
  • Right-Click to bring up the Start Context Menu.
  • Click Programs and Features.
  • Locate The certificate is not trusted because the issuer certificate is an unknown-associated program (eg. Firefox) under the Name column.
  • Click on the Firefox-associated entry.
  • Click the Uninstall/Change on the top menu ribbon.
  • Follow the on-screen directions to complete the uninstallation of your Error sec_error_unknown_issuer-associated program.
  • After you have successfully uninstalled your Error sec_error_unknown_issuer-associated program (eg. Firefox), reinstall the program according to the Mozilla Foundation instructions.

Run Windows System File Checker (“sfc /scannow”)

System File Checker is a handy tool included with Windows that allows you scan for and restore corruptions in Windows system files (including those related to Error sec_error_unknown_issuer).

To run System File Checker (Windows XP, Vista, 7, 8, and 10):

  • Click the Start button.
  • Type “command” in the search box… DO NOT hit ENTER yet!
  • While holding CTRL-Shift on your keyboard, hit ENTER.
  • You will be prompted with a permission dialog box.
  • Click Yes.
  • A black box will open with a blinking cursor.
  • Type “sfc /scannow” and hit ENTER.
  • System File Checker will begin scanning for Error sec_error_unknown_issuer and other system file problems (be patient – the system scan may take a while).
  • Follow the on-screen commands.
  1. Install All Available Windows Updates:

Microsoft is constantly updating and improving Windows system files that could be associated with Error sec_error_unknown_issuer.

To check for Windows Updates (Windows XP, Vista, 7, 8, and 10):

  • Click the Start button.
  • Type “update” into the search box and hit ENTER.
  • The Windows Update dialog box will appear.
  • If updates are available, Click the Install Updates button.
  1. Perform a Clean Installation of Windows

Reasons of Error sec_error_unknown_issuer:

  • Corrupt download or incomplete installation of Firefox software.
  • Corruption in Windows registry from a recent Firefox-related software change (install or uninstall).
  • Virus or malware infection that has corrupted Windows system files or Firefox-related program files.
  • Another program maliciously or mistakenly deleted Firefox-related files.

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