Astonishingly, the private keys were 4, 56, 66, 115, 155, 156, 230, 237.
exploiting compromised certificates requires an active adversary-in-the-middle attack, meaning the attacker must act as a proxy between two TLS parties and receive encrypted traffic, decrypt it, reencrypt it, and send it to the other party. Such capabilities, in some cases, are usually limited to only the most well-resourced attackers. People with control of a local network—at a coffee shop, university, or other organization—face much less of a challenge.
https://emudhra.we-have-a-problem.com/
I did try with Fennec from F-Droid, which was fine. I updated Nightly just now, and it does still connect.
Edit: Firefox Beta connects to 6/12 on https://emudhra.we-have-a-problem.com/
Edit 2: Regular Firefox connects to 0/12
Edit 3: Latest update fixed this in nightly, I haven't checked beta.