I also use the paytm app with a very ease, but there are some vulnerabilities I observed as a user, like money management. As the money management is online so I always think the insecurity issue regarding the card details. When someone log in it on a particular device it saves cookie and next time login information, and most of the times it even doesn’t sends OTP on the phone. It has a feature of saving the card details for faster checkout.it can be misused. The customer service of paytm is very poor. When your money gets stuck anywhere due to some problem, they have a trouble shooting management and in case if it happens then the customers has to suffer badly.
The concept of this app is not bad but it should provide some security so that the customers should feel free to make payment.