My money is on an American gadget installed in embassies, perhaps telecommunications. Of course they can't acknowledge or say anything.

Seems something was said of it. Most being unlikely, indicates that the remaining cases are likely to be caused by say national agencies.

Never take public CIA statements at face value. They say what they want to irrespective of reality and facts.

If what is happening is caused by classified American tech they won't say anything and will find some other "plausible" explanation and my guess is that this is exactly what they are doing. Heck, they may do that even if they know it's caused by a foreign government.

That's the thing with this sort of topic and intelligence agencies: you cannot trust anything you're told.