https://news.ycombinator.com/item?id=6166731
- dump all your session cookies
- grab your history
- install malicious extension to intercept all your browsing activity
- install OS user account level monitoring software
The last one could plausibly work, in combination with "grab a copy of the encrypted 1Password key file", to compromise all the 1Password stuff. The others essentially work around 1Password, or so I believe.
This is why there are certain passwords that I don't even store in 1Password. It's also an argument for two-factor auth.