Question about CDS and CDX

I am a little confused about the long and short in the CDS and CDX…
I want to clarify that in CDS, long is actually a seller and short is a buyer, however, in CDX, long is a buyer and short is a seller,is that right?
Since when I was doing the Reading practice problems, when it mentioned CDX, the answer still said that CDX’s long is a seller, I am really confused.