Tl;dr: change your master password.
LastPass says in its blog entry, "Encrypted user vaults were not compromised." This is a critical fact because changing your master password will immediately make the stolen password information useless. If crackers had stolen vaults, they would be able to churn on them forever or return to them to the future and crack them with more advanced or powerful technology. Since people often don't change passwords for years at a time or forever, that could have still been a risk.
LastPass also advises changing your password at any other account for which you use the identical password