In ST:DIS 1x10, "Despite Yourself", when Tyler sees Dr. Culber in sickbay, Stamets
who is catatonic at the time and only briefly gains consciousness
tells Dr. Culber
"Be careful! The enemy is here!"
Dr. Culber then examines Tyler and discovers
that Tyler's body was surgically altered. (Tyler is a Klingon, Voq, and immediately kills Dr. Culber upon that revelation.)
How did Stamets know anything about that? His connection to the spore network gave him some knowledge via his
mirror universe counterpart
which is, for instance, why he instinctively called Tilly "Captain" once.
But what could he possibly know about
Voq/Tyler, given that the Voq in the mirror universe is the leader of a rebel faction and was not altered into appearing human?