For the past three days, DNS lookups for codemirror.net subdomains have been mostly failing. Some clown has been hammering my hosting provider with a DDoS attack on their DNS (using random codemirror.net subdomains), which caused them to blackhole all such requests, making it impossible for people’s browsers to find discuss.codemirror.net or lezer.codemirror.net (the root domain was not affected).
Sorry about the inconvenience. I initially expected the attacker to get bored of this pretty soon, given how little they have to gain from this, but I guess botnets are cheap enough these days to keep such a thing up for a while, seeing how the attack is still going strong at this moment.
I’ve moved the domain to a more abuse-resistant provider, which seems to be working. Not all DNS servers have picked up the move yet, at this point, and it might take another 10 or so hours for everybody to have access again.