India, July 3 -- Millions of people have watched the videos: a prankster taps a smartphone screen, and a moving e-rickshaw abruptly grinds to a halt. The drivers appear confused while the people filming laugh. On the streets, though, this social media 'trend' has created a real hazard.

Behind the jokes is a basic flaw in how some electric three-wheelers are built. Many modern e-rickshaws use Bluetooth-enabled battery systems. To monitor battery health, manufacturers use apps like BAT-BMS and Lossigy.

Some of these systems were built without any password protection or authentication. Anyone within Bluetooth range can download the app, connect to a nearby vehicle, and cut its power with one tap.

In a test conducted by Hindustan Times wit...