False ground on plug-in GFCI device?
I have a plug-in GFCI device that plugs into a receptacle and has 6 outlets. I have it plugged into a receptacle that I know to not be grounded. Yet, when I plug in one of those 3-prong receptacle testers with 3 lights into the GFCI device, the tester indicates that it is correctly wired with a ground. Also one of those probe things with a light lights up when the probes are inserted in the hot slot and the ground hole. I don't see how this could be happening unless the GFCI device is wired internally with a false ground, i.e. a connection between the ground hole and the neutral slot. Another GFCI device I have from the same company tests as I would expect, showing an open ground. My question is, is it possible that someone would intentionally manufacture a device with a false ground? Is this device dangerous to use?