I only stored that LastPass master password in a KeePass file that I keep local and (obviously) encrypted. I hadn't logged into to that LastPass account since

I only stored that LastPass master password in a KeePass file that I keep local and (obviously) encrypted. I hadn't logged into to that LastPass account since 2017. Hence, I presumed that my KeePass file might have been compromised, but it seems unlikely now, considering many other people (6? 7?) are coming to this thread with a similar story of their master passwords being known to the "Brazil" attackers as well. i.e. our master passwords have been leaked. By when? And by whom?