So LibreOffice can still make arbitrary HTTP/HTTPS connections without the users knowledge? Unless WEBSERVICE URLs are disabled by default, this doesn't sound like a complete fix.
> bringing WEBSERVICE URLs under LibreOffice Calc's link management infrastructure.
Sounds like using WEBSERVICE should trigger a warning, although I'm not sure if that is what "link management" means.
a) after the document is loaded such use triggers the "links to other documents" warning and linked content is updated only after confirmation