I am getting the "Your connection is not secure" for most sites running Firefox 49.0.1. I know that it is related to not accepting SHA-1 certificates, but this is on a work computer that is setup to force users to communicate through a proxy to the outside world. It is essentially using a man-in-the-middle approach to filter all data to and from the internet, and is not something that I have any control of. This proxy uses a self-signed certificate, using SHA-1. For more recent Firefox releases, it worked well enough to put the proxy's certificate into the trusted authorities of the Certificate Manager. For this release, I don't see the previously added certificate, nor does it show up when I try to add it manually. Also, I have tried playing with the security.pki.sha1_enforcement_level preference, it doesn't have any effect on adding this certificate as an authority or allowing access to sites like google.com or mozilla.com. I am all for better security, and this version of Firefox works just fine at my home. But at work, I don't have much recourse, since Firefox isn't really supported by IT here. Really, the only thing I can do is switch to Chrome or IE if I can't get this resolved.