Not a specific security breech, but there is this:
https://www.cnn.com/2019/09/09/politics/russia-us-spy-extracted/index.html
In a previously undisclosed secret mission in 2017, the United States successfully extracted from Russia one of its highest-level covert sources inside the Russian government...A person directly involved in the discussions said that the removal of the Russian was driven, in part, by concerns that President Donald Trump and his administration repeatedly mishandled classified intelligence and could contribute to exposing the covert source as a spy.
But, but... her emails!
One is sneaky, one is an idiot.