You can bypass Chrome’s warnings; if you click “Details” on the big red page, you can click through to “visit this site” and you’ll reach the download page.
Of course, Chrome will then say the custom file itself is dangerous and try to stop you from downloading it, but if you open the Downloads tab (Ctrl-J) you can tell it to go ahead with the download.
But… yeah that’s all pretty annoying, and more often than not Google’s not too bad about blowing the whistle, and there’s no way to whitelist C3 and keep the warnings on normally. There is, though, a means by which a site that’s been marked can petition to no longer be flagged.
https://developers.google.com/web/fundamentals/security/hacked/request_review
