I remember a lot of low number ICQ accounts being taken over back in the day, including my own and several security-minded friends. Because of how prevalent it was and how it was the only account we'd had compromised we assumed they found a flaw or had access to reset passwords, or could social engineer support etc.

It's good to finally know there was a critical flaw like the one in OP that was likely used.

Mine was in the 3.5 million range. My roommate at the time had a 6 digit number and didn't sign up that much before me, I remember it felt wild that they had grown so quickly. And then not long after that it was all 8 digit numbers.

And also yes, the last time I looked, my account was all cyrillic.

In my case because I use it as a random seed or parts of it as PIN, cause I will never forget it and it's "secret" enough.

More importantly: Are you and your girlfriend still in contact with each other today?

Mine was 8966646, which is cool because it has 666 in it.