I helped draft the original blog post :-) To clarify a bit more and help folks evaluate their individual risk, it's worth noting that the impact is limited to a fairly specific scenario.
In essence, you needed to have a non-native document format uploaded to Drive without converting it (PDF is a good example); explicitly share this document with others using a particular setting ("anyone with the link"); and then preview it in the web UI and follow an outgoing HTTPS link (HTTP wouldn't be a problem).
In essence, you needed to have a non-native document format uploaded to Drive without converting it (PDF is a good example); explicitly share this document with others using a particular setting ("anyone with the link"); and then preview it in the web UI and follow an outgoing HTTPS link (HTTP wouldn't be a problem).