Firefox has been my favourite browser for some time because of its low memory footprint and wide range of plugins. However it is now shooting itself in the foot.
Since version 43 it has been requiring plug-ins to be signed. This is good for security but because some of the plugins that I use are not signed means that I can’t use them thus negating Firefox’s main advantage.
I have also started using Windows 10 parental controls on my children’s PCs. Unlike Microsoft browsers and Chrome, Firefox does not keep its certificates in the Windows certificate store and as a result if parental controls are enabled cannot visit an https site without prompting “untrusted connection”.
This might explain why I get so many “untrusted connection” prompts from Firefox when working within a client’s firewall in spite of the fact that I accept the prompt to add the firewall certificate to my Windows certificate store. It may be necessary to update the Firefox certificate store with the firewall certificate rather than the Windows certificate store.