I've gotten the same warnings, too, ever since I came back this year (Firefox user; Chrome's 666 logo weirds me out). I'm unable to connect via HTTPS at all, meaning all login credentials, PMs, etc are going unencrypted across the world's routers (not that I reuse passwords, so the security risk to me individually is negligible, but still...). Not sure if the site is missing a cert entirely (they can be had from Let's Encrypt for free), or if the server is only configured for obsolete protocols (SSL or older TLS versions).