I had a knockoff laptop power supply energetically self-disconnect. That was surprising!

Laptop was plugged in, cord draped over something and under mild tension. As near as I can tell, the wires shorted on the DC side, instantly melted the plastic insulation, and suddenly I had a severed cord and two live wires sticking out of the brick.

... so no, I would never leave a counterfeit laptop charger unsupervised.