That explains why one of my IoT vendors is using an expired certificate. I wish Firefox would just give a mild warning for a recently expired certificate, instead of treating it the same as a true man-in-the-middle attach. It's not like someone who couldn't factor the private key in 200 days could in 201 days or even 300 days. I'm convinced that we'd have better security, if we didn't have so much security theater. Y…
The IoT should have updated the certs weeks in advance. If they haven't done it by day 0 then their process is broken and delaying the scary warning to say day +5 won't solve anything.