Same here except in Chrome - error is NET::ERR_CERT_AUTHORITY_INVALID and issuer is "Cisco Umbrella Secondary SubCA chi-SG". Windows is saying "the issuer of this certificate cannot be found".
You (or your employer) have Cisco Umbrella, which is MITMing your network connection. You can read about Cisco's Umbrella product by Googling for it. You should comply with your employer's rules about non-work browsing. You could try asking IT support to "fix" the problem if you want, although if what you're doing is against policy they probably won't.
Or - very much less likely - a bad guy is attempting to MITM you and they've decided to imitate Cisco Umbrella so that people aren't interested in helping you because they assume you're just at work goofing off on someone else's network.
Good info - yes my employer MITM's certs, but this is the only site I've run into with this. If I visit a site which violates policy, there's an error page that specifies which policy has been violated, it's not an obtuse cert error.
