When Becky meets Simon in the cube, they hug, then Simon literally stabs Becky in the back. As she falls down to the floor, her black shirt reveals not only some of her chest, but part of a black microphone wire.
When Kate and Sasha are talking and Kate says "Please, you have to have some idea what this means.". At that time you can see an alien looking person moving reflected in the walls. It moves into view, stops for a second and moves out of view again. This is not Kate because she is standing on the other side of the room. There is also a quiet sound effect as it shows itself.