Are you implying that browsers save passwords in cleartext? A quick search indicates that all major browsers encrypt passwords to user accounts, and some give the option of a master password as well.
They do encrypt passwords but that doesn't matter. You can still log in to their accounts and do anything you want. And if for some reason you really do want the actual passwords you can obtain those too, obviously they get decrypted to send to the website you're logging in to so just capture it at that point. Normal people don't configure master passwords.