If you're having website connection issues after a Firefox update, your third-party antivirus software, such as Avast, might be interfering with Firefox's secure connections. <!-- https://bugzilla.mozilla.org/show_bug.cgi?id=1523701 SEC_ERROR_UNKNOWN_ISSUER since updating to Firefox 65 --> We recommend uninstalling your third-party antivirus software and using the security software offered for Windows by Microsoft: * Windows 8 and Windows 10 - Windows Defender ([https://www.microsoft.com/windows/comprehensive-security built-in]) For more information and other solutions, see [[How to troubleshoot security error codes on secure websites]].