I just went to r&d’s websight with Firefox and Safari on my iPad. I did not get the warnings posted about.
I’ve seen that when a security certificate on a website has an issue or is “out of date”. Or, some browsers will give you a warning if it’s not using https which is HyperText Transfer Protocol Secure....
I’d agree with some kind of update happening, or it was caught just at the right time when the certificate expired.
Also as mentioned, I’ve seen funny thing happen, especially with something that you have to sign in to, like a bank app, if you are bouncing back and forth from WiFi to cellar data. It thinks you are someone else and blocks you.