John Morehouse shows you how to fix plaintext password storage when you can’t fix the application:
Once the data has been encrypted, we can move forward with creating a new view that will be used to “head fake” the application. The view is named the same as the original table therefore the change is seamless to the application. The application doesn’t know if it’s calling a table or a view so that’s why this works.
You should never store passwords in plaintext. You should almost never store passwords in a reversable format (i.e., encrypted). The primary case in which I can see storing passwords encrypted rather hashed is if you have automated systems (or non-automated technicians) which need passwords to authenticate somewhere. Even then, there’s a lot of value in using OAuth tokens. But if you can’t get around any of this, John’s solution does remove the really bad decision of leaving passwords in plaintext.