Add a note to dotnet nuget add source

[Youssef1313]

FYI @gewarren

cc @mmitche if you want to add more details.

[IEvangelist]

I'd like to have @blowdart chime in here for the correct course of action - thank you.

I wonder if linking to something like this is more appropriate? https://docs.microsoft.com/nuget/concepts/security-best-practices

[blowdart]

The intent is good but linking to news articles is bad. Instead, consider linking to the whitepaper, through its aka.ms link, wrapped in the warning chrome?

Care should be taken when adding multiple feeds not to introduce a dependency confusion attack.

[blowdart]

That works, I leave it to @IEvangelist to chime in on wording :)

[tdykstra]

Thanks, @Youssef1313 !