(In reply to :Felipe Gomes (needinfo me!) from comment #2)
Really old regression, with a simple work around for the user (pasting in the URL bar instead of the Downloads window).
So while it would be nice to fix, I don't see us taking on this work in the near future
No, that is different.
Pasting the URL into URL bar will load and display the document in the browser window, instead of downloading and saving to filesystem.