If you try to log in from a meta site (
meta.*.stackexchange.com), you get an "Untrusted Connection" from Firefox, even without HTTPS Everywhere enabled.
For example, I just tried this on
meta.law.stackexchange.com and the certificate appears to be only valid for
ssl8217.cloudflare.com, *.stackexchange.com, stackexchange.com domains, thus causing
It has been over two years since this issue was reported, and it continues to appear.
Here's one version of the security warning, on Firefox:
It's 2016, and we should be having reliable HTTPS coverage by now, at least for login.