Yesterday I checked Czech websites in “Collection #1” and others (like “Collection #2” to “Collection #5”, “BigDB”), today I've checked Slovak sites. We're neighboring countries and historically have a lot in common, many Czech users have accounts on Slovak sites as well, so it seemed like a good idea.
Last week was all about the 773 million records data breach, nicknamed “Collection #1”. It's a few years old compilation of previous data leaks but it's still interesting to check which Czech websites (and Slovak, too) are present in this and other databases (like “Collection #2” to “Collection #5”, “BigDB”).
You don't crack passwords using rainbow tables or brute-force attacks anymore. So this probably wasn't a plaintext leak, somebody have cracked 750k passwords and uploaded them online. I've tried cracking them too.