At least after synchronization, my passwords are stored on the Avast servers.
Question1: Is it possible to access this information online, e.g. when I log into my account?
Question2: I fear that the Avast Password store might be compromised.
Question3: Do you keep of deleted passwords? (and keep them stored on your servers)
Answer 1: No it is not
Answer 2: This is hard to answer, technically anything can be compromised. With bruteforcing there is no chance to break the storage. With social engineering (guessing your master password) it is possible of course as in any other case when you protect something by key only you know.
See our security whitepaper to get picture about encryption model we use
https://files.avast.com/files/passwords/security-whitepaper.pdf
Answer 3: No we don’t, once you delete the password is it gone and is no longer in data set thus neither in synchronization