LastPass is an evolved Host Proof hosted solution, which avoids the stated weakness of vulnerability to XSS as long as you're using the add-on. LastPass strongly believes in using local encryption, and locally created one way salted hashes to provide you with the best of both worlds for your sensitive information: Complete security, while still providing online accessibility and syncing capabilities.
On Windows, LastPass helps find insecure passwords stored on your computer so you can store them securely in LastPass and remove the easy access by malicious software. LastPass uses SSL exclusively for data transfer even though the vast majority of data you're sending is already encrypted with 256-bit AES and unusable to both LastPass and any party listening in to the network traffic -- the amount of data is trivial so the extra encryption doesn't hurt. Our policy of never receiving private data that you haven't already locked down with your LastPass master password (which we never receive and will never ask for) radically reduces attack vectors. We use firewalls and best practices to protect the servers and service, but our best line of defense is simply not having access to data even if someone got in. If LastPass can't access it, hackers can't either.