Today I was greeted by this error in Firefox:
It was happening consistently for a minute or two, and reverted back to normal. I confirmed that it happens on another browser and that other HTTPS sites open up properly. I wasn't able to check what happens on other devices on my network before it went back to normal, however I did ssh to another machine outside of my local network and attempted to
curl google.com (all OK).
I'm on a home network behind a NAT using a wireless router (Cisco EPC3928) that my ISP (Vectra, PL) is remotely controlling.
What are the possible causes for what I'm observing? I don't suspect it's Google's fault.
I wasn't able to find any info about the domain xn--ngstr-lra8j.com that shows up in the cert.