An injection attack on a download is not one of the problems we're actually talking about here. That's a problem that affects any package manager.

And it's patently false to say that the deploy plugin documentation encourages you to include that information. They very clearly preface that with "if your repository is secured" and use the explicit example of an internal repository within a corporate context. People smart enough to read that documentation in detail should also be smart enough to determine when it is and isn't a good idea to do that.