Your Kaspersky software has a feature to scan your web traffic for threats. This is seamless with non-secure sites, but with secure sites, the program has to present Firefox with a fake certificate so it can decrypt your request and the site's response.

One option is to turn off "Scan Encrypted Connections", or make an application-specific exception for Firefox. But if you want the benefit of scanning, the better option is to add a certificate from Kaspersky to Firefox so Firefox no longer objects to the fake certificates.

I haven't looked up the latest documentation, but here are some articles on this feature from earlier versions:

• General SSL scan setting: How to scan encrypted connections in Kaspersky Anti-Virus 2012?; How to scan encrypted connections in Kaspersky PURE 2.0?

• Making an exception for a specific program (e.g., Google Chrome): Encrypted connections scan by Kaspersky Internet Security 2012 in Google Chrome; Scan of encrypted connections in Google Chrome and Opera (KIS 2013)

Thank you for the help. I was able to find the Kaspersky certificate and ran the installation wizard automatically. It shows that the certificate should work with Firefox, but it has not fixed the problem. I did not do a manual install.

Any other ideas? I really don't want to remove the scanning function.

Thanks.

Hi medeed, I don't have this software, but assuming it added the certificate to Firefox's certificate store automatically, I would expect it to show up here:

"3-bar" menu button (or Tools menu) > Options > Advanced > Certificates mini-tab > "View Certificates" button > Authorities tab

It probably is necessary to import the certificate to this tab manually if it wasn't added automatically. Did you find the steps?

The certificate is there. Also, I have used Kaspersky and Firefox together for about 4 years without incident. It seems to me that the problem would not be related to what seems to be a basic set up issue. Could something have changed to make their cert invalid? Dates and times on my computer are good.

In the Technical Details section of the error page, what is the explanatory code, for example "sec_error_unknown_issuer"?

Strange because I've checked this daily and have done nothing to fix the problem, but today I had no problem signing into email. Any thoughts?

Hey there,

Have you changed WiFi networks? For instance, were you on holiday and have come back, were you at work the first few times and at home the last, etc?

Thanks!

Curtis Parfitt-Ford Mozilla Support

Kind of interesting. I use cable set up in house and also a portable modem. The problem began on the in house system, but I also experienced it under the modem, both with Firefox. On a different pc with Internet Explorer I was able to log in with the modem, but not with the in house system. In the latter case I did not get any error message other than the page could not load.