This is a very sophisticated attack!
https://www.theverge.com/2017/5/3/15534768/google-docs-phishing-attack-share-this-document-with-you-spam
But Google seems to have mostly stopped it:
https://www.reddit.com/r/google/comments/692cr4/new_google_docs_phishing_scam_almost_undetectable/
I don't use Google Docs but still, hacks like worry me because basically, we're all in this together.