This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Problem displaying https websites (sec_error_unknown_issuer)

more options

Lately I have upgradet from Windows 8.1 to 10. First it seemed all right. But when I opened Firefox and wanted to open Google.com I got the error sec_error_unknown_issuer. First I cleared my cache. But It didn't work after that. So I deinstalled Firefox and installed it again. The error message is still there.

Lately I have upgradet from Windows 8.1 to 10. First it seemed all right. But when I opened Firefox and wanted to open Google.com I got the error sec_error_unknown_issuer. First I cleared my cache. But It didn't work after that. So I deinstalled Firefox and installed it again. The error message is still there.

Chosen solution

Sorry for the hassle. Many users are updating their security software or enabling parental controls during or shortly after their Windows 10 upgrade, and Firefox may need to be set up to work with those changes.

Do you use Avast, BitDefender, ESET or Kaspersky security software?

If not, could you try disabling Microsoft Family Safety: http://windows.microsoft.com/en-us/windows-10/turn-off-microsoft-family-settings

Read this answer in context 👍 2

All Replies (3)

more options

Seçilmiş Həll

Sorry for the hassle. Many users are updating their security software or enabling parental controls during or shortly after their Windows 10 upgrade, and Firefox may need to be set up to work with those changes.

Do you use Avast, BitDefender, ESET or Kaspersky security software?

If not, could you try disabling Microsoft Family Safety: http://windows.microsoft.com/en-us/windows-10/turn-off-microsoft-family-settings

more options

jscher2000 you're a genius !!!

I don't use Avast, BitDefender, ESET or Kaspersky security software. So I tried with the family safety. After logging in to my account I noticed I was added to a family. After I removed myself from it I tried to open google again. Now it works without any problems.

Thanks for the quick response.

more options

I can't claim credit. This is about the fifth day of Windows 10 users having the same problem, so by now we have a good idea of what to check.