https://www.w3.org/TR/security-privacy-questionnaire/
Yes: IP addresses. In addition, it could be used to communicate personally-identifiable information.
Yes. See 3.1.
3.3 Does this specification introduce new state for an origin that persists across browsing sessions?
No.
Yes. The proposed capabilities of the API would allow a web application to bypass CORS and CSP checks.
3.5 Does this specification expose any other data to an origin that it doesn’t currently have access to?
Yes. If permission is granted, the proposed API could be used to send and recieve arbitrary data.
No.
Yes, in the form of imprecise IP location data.
No.
3.9 Does this specification allow an origin access to aspects of a user’s local computing environment?
Yes. It would allow access to the public and (if applicable) private IP addresses of the device.
No.
No.
Yes. If the network was configured with DHCP, the proposed API would allow access to the public and (if applicable) private IP addresses of the device.
No.
No change in behavior.
No.
Yes.
Yes. If permission were granted by the user, the proposed API would allow communication of arbitrary information to and from arbitrary origins, sidestepping CSP and CORS.