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Firefox secured sites are not loading with Avast installed.
None of the Firefox sites are working. Google, Yahoo, all the major sites are not working. It displays error page "This Connection is Untrusted". Technical Details: Error code: sec_error_unknown_issuer
I have the latest version of Firefox installed (43.0) on a new Macbook Pro on El Capitan. I presume the problem is with Avast installed and they are not talking correctly to each other. All my other web browsers work fine, it is just with Firefox.
Once I disable "Scan secured connections" in Avast, all works fine. Is this an Avast issue or Firefox issue?
All Replies (2)
There is security software like Avast and Kaspersky and BitDefender and ESET that intercept secure connections and send their own certificate.
If you have Avast then try to disable HTTPS scanning in Avast Web Shield.
Avast is designed to set up Firefox automatically, but this doesn't always work. If rebooting your Mac doesn't trigger Avast to add its signing certificate to Firefox, maybe you can find steps in the Avast forums to do it.