How can I detect current direction?

sofakng

I'm trying to read how much current an HDMI Hybrid Fiber cable is using.

I'm using an HDMI power injector that injectors +5V power from a USB power into the HDMI connector.  However, when I plug the power injector into the CT-3 (female USB port), the CT-3 turns on.  Why is it backfeeding power from the device (HDMI power injector) and can I disable this?