Authors of this blog received the following from a very useful extension:
Dear LastPass User,
We wanted to alert you that, recently, our team discovered and immediately blocked suspicious activity on our network. No encrypted user vault data was taken, however other data, including email addresses and password reminders, was compromised.
We are confident that the encryption algorithms we use will sufficiently protect our users. To further ensure your security, we are requiring verification by email when logging in from a new device or IP address, and will be prompting users to update their master passwords.
We apologize for the inconvenience, but ultimately we believe this will better protect LastPass users. Thank you for your understanding, and for using LastPass.
The LastPass Team
We will be updating ASAP