Very low (when connected to the input impedance of the meter anyway).
Keep in mind that the output is a current and that the open circuit voltage will be limited by saturation of the CT core.
For the CTs it will depend on the burden and rating but tens to hundreds of volts is within accuracy range. If open circuited (don't do it!) it can spike thousands of volts and that is why we short out the CT secondary when not connected.