Since your master password is stored in another password manager, would it be accurate to say you copy/paste it into LastPass? If so, something running on your machine could be scraping your clipboard. This of course assumes that it wasn’t really you from an IP that was just misidentified as being from Brazil. For what it’s worth, I stopped using LastPass after they sold out to LogMeIn and would recommend others stop…
Why do you recommend others to stop using LastPass?
1. BW supports inline Android 11 password fill. I find the UX much better with this feature
2. LP is a bit buggy, particularly on Android
3. LP is slow to add new features
4. I didn't expect this, but I really enjoyed BW's UI
5. On Android, I enjoy the three quick launch buttons they provide
6. LP creates new logins in folders of it's choosing by default. Not a fan
But in general, BW it just "works" better/faster for me