Comment by andrewmcdonough

That's good advice. I already made that assumption when the leak was first publicised and changed all of my important passwords the same day. I'm just trying to decide whether it's worth changing the hundreds of other low value passwords that were once stored in LastPass. I migrated to another service a few years ago, but I'm concerned the attackers have got hold of older backups, containing sensitive data that I had deleted, but with LastPass's poor communication, there is no way of knowing.