A staffer put a journalist in a group chat...
in which Cabinet members were discussing S//NF details that, through compilation, add up to TS//NF information on a non-secure information system.
So, you're blaming the staffer for adding a journalist, and not the multiple Cabinet members who actually did the illegal thing in question?
Luckily, the journalist had the presence of mind to wait until after the operations were concluded before publishing the story. A *I poop my pants, don't laugh at me* load of American service members could have been killed.