this is why I use a password manager that has no network connectivity whatsoever, and no browser integration. keepassx with a v2.0 keepass format file.

it works from a local file on disk. yes, it's more inconvenient if I am away from the computer it lives on, and I need to update a password, I have to connect the VPN to my home office, ssh to it, and run 'kpcli' (a keepass format command line program), or run keepassx in a vnc-over-ssh session.

but that hassle is worth it in my opinion.