Can't access login pages ERR_CERT_INVALID

You need to have a way around invalid certificate errors so we can actually access WiFi sign-in pages. The error is NET::ERR_CERT_INVALID, and the blurb for it even says “This may happen when an attacker is trying to pretend to be www.google.com, or a Wi-Fi sign-in screen has interrupted the connection.”

But there’s no way to, you know, access that WiFi signin page. Which is necessary, of course. Firefox does it, maybe copy their method