Firefox developer edition insecure connection all the time

Question

Just installed FDE at my work, but I get the following message when trying to visit youtube.com, google.com and sites:

Your connection is not secure

The owner of www.youtube.com has configured their website improperly. To protect your information from being stolen, Firefox Developer Edition has not connected to this website.

This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox Developer Edition only connect to it securely. As a result, it is not possible to add an exception for this certificate.

What the hell is this? How can I fix it?

Currently my FDE network settings are "No proxy", I have not touched anything about certificates or stuff in the security tab.

Hope you guys can help, since I like the browser.. but maybe not for long.

Answer 1

Found a solution.

The issue was "AVAST Mac Security", as described in this article: https://support.mozilla.org/en-US/questions/1032509

The problem was caused by the following (copy paste from the link above):

in order to be able to decrypt and inspect your communications, the software needs to present a fake certificate to Firefox

So when i uninstalled AVAST and rebooted my laptop, everything was fine :-)

Answer 2

I had the same problem. Duck Duck Go, Start page, Google almost all the search engines except for Amazon & eBay, had the same message. I found script on the browser settings? Deleted it and the problem went away? The file was strange as was the script. It looks like some one has gone through a bit of trouble to write this as it effected so many browsers on a Linux system, Even bypassing the anti virus search clam Win and another I can not recall. The script actually had the name of the anti virus on it with commands to ignore or not show a positive reading.