A while back I used the online platform of a local bank to buy some shares. I then sold the shares soon thereafter and withdrew my cash. However, I checked the stock balance which remained unchanged. I sold the stocks again, and sure enough, money reflected on my account again, and the stock balance remained. I have tried withdrawing the cash and sure enough, it can be withdrawn although deep down, I know that the cash isn't mine. What should I do? Should I alert the bank to patch this vulnerability or should I just shut up and keep withdrawing which is essentially, theft?