Wikileaks is a provider of primary sources, like any good historical archive. In this case it's providing a PDF of the Minton report. The summary Wikileaks provide is, of course, a secondary source, but people are linking to the page because it hosts the PDF, not because it happens to summarise the contents of the report and its historical context.

The Guardian, reporting on the Trafigura case, are a secondary source (when referencing the report), and a primary source when writing about the gagging order that has been applied to them. The Spectator blog article is a secondary source writing about the gagging order. These distinctions are standard in both historiography and journalism.