The ExtendedEBIS upgrade is being developed at Brookhaven National Laboratory to replace RhicEBIS. ExtendedEBIS consists of two series solenoids to allow increased trap length and to accommodate an internal gas injection system in the upstream solenoid. An insertable electron beam detector is installed between the solenoids. The detector comprises two sets of quadrant plates placed on either side of a base plate. Each set of the quadrants has an (8.5 mm) aperture, larger than the beam diameter (4.5 mm) at that location. By comparing the 4 signals from any intercepted losses on the cathode facing side, the pulsed electron beam position can be monitored. Therefore, one can continuously adjust the electron beam radial position at the axial midplane of Extended EBIS system without stopping the beam. The detector is useful for the beam alignment during commissioning and for checking the transverse beam steering system during operations. The set of the quadrants on the collector facing side is used to measure the electrons back-streaming from the collector or collector suppressor electrodes. During this presentation, the detector design and electron beam test results will be discussed.