Will this create any security exploit?

I've a mongodb collection "users" in which i want to add a new field "wallet_amount" when user add money in their wallet. Right now at the time of user registration, i'm trying to insert a document like this

db.users.insert( { email: "test@test.com", wallet_amount: 0 } ) 

Is this the correct way of doing this or there are chances this will create some security exploits since i'm passing wallet_amount default value as 0? Or wallet_amount should be inserted only at the time when user add money in wallet.

via user3588408