I'm not entriely sure of what is involved and what could be done with this data but it is possible to export your keychain data
Keychain Access: Import and export keychain items
if you dont use Keychain (and some of us, including me don't) then those "•••••••• "passwords are not transferable.
someone might see them as ••••••••• in a login windows but f they paste them the don't appear as plain text passwords, at least they shouldn't.
You are far more likely getting hacked by using the same password for one on line service as you do for others, and if that gets hacked someone only needs to guess that you use the same one for Apple or Amazon or whatever and try that combo on a site and see if it "unlocks the door" for them so to speak.
As I said if you suspect an Apple employee or someone who is supposed to represent an Apple Authorized Repair Center is using your credentials against your discretion you need to contact Apple. In the mean time if you are concerned you should change those passwords and remove the possibility of access with the previous credentials.