ADDTrust External CA Root certificate expired I'm running El Capitan (macOS 10.11.6, 15G22010) with Safari 11.1.2.

The ADDTrust External CA Root certificate expired today. This broke Safari navigation for many sites. Firefox and Chrome work fine on the same sites.

Can Safari navigation be fixed?
Same issue here; a temporary (not production-ready) fix is to set back your system date.