One of the contractors who got access to the data was employed by the Serbian military for a decade. I suppose you are aware of the ties Serbia and its military has to Russia? It's not unprobable that this guy sold the information to Russia. Even if not, Sweden must treat a potential leak like this as a real leak, or else risk endangering their operatives.

Oh, yeah. The leak is _still_ ongoing: https://translate.google.com/translate?hl=en&sl=auto&tl=en&u...

More info here, with Google translated for your convenience: https://www.privateinternetaccess.com/blog/2017/07/swedish-t...