Can my xbox one be accessed by the previous owners pc?

I would also go to security and privacy and make sure you have passwords and possibly two factor authentication going.

An Xbox One can not be externally accessed outside of the
gamestreaming feature which will clearly pop up a message. This only works if the same account is logged in on both the Xbox and the

gamestreaming device. If the previous account is still present on the Xbox I suggest removing it.

https://support.xbox.com/en-US/my-account/manage-gamertag-and-profile/add-remove-account-xbox-one

no, they shouldn't be able to access your Xbox, but if you want peace of mind you can do a Factory Reset to delete all accounts, saved games, settings, and home Xbox associations.

this link will guide you through the process, but make sure you have your account email and password as you will need to add your account back on to your Xbox after the reset.

https://support.xbox.com/en-US/xbox-one/console/reset-console-to-factory-defaults

you can select the option to keep games and apps so that you don't need to download them again.

hope this helps

it may also still be set up as the previous owners Home Xbox. If your friend bought it with access to digital downloaded games, the shock will come once the owner makes their new Xbox as the home one. Digital games can not be transfered to a new owner.

It sounds like you bought a used Xbox and the previous owner bought a new/different Xbox, once he made that new one his home console, you lost access to the previous games. At least, that's my educated guess on the matter.