More specifically, we know:

- other possible sources in the area have a history of cooperation, so process of elimination is rather suggestive.

- Russia has leaked and not come clean before, so history is also rather suggestive.

But who knows! It has already been a very weird year, anyone want to bet it can't get weirder?

> Russia has leaked and not come clean before

Russia or the USSR?

Russia, in 2017. https://www.nytimes.com/2017/11/21/world/europe/russia-nucle...

Same leadership, different labels.

Also true for the US...hi Nixon ;)

https://www.armscontrol.org/act/2019-09/news/us-completes-in...

When that USSR anthrax factory started leaking at least it wasn't contagious.

Well, there's very few places in the area where this could come from and Russia has a history of lying like a rug about pretty much everything. So there's that.