Keeping things vague - I work at a company that handles compliance issues for our clients. Very often, this means we need to log onto their various accounts for various entities. We store their username and password, both to make it easier for them to remember and have access to, and for us to be able to log onto their account.

Ignoring the complete and total security nightmare of sharing logins for a minute, the username and passwords appear to be stored in plaintext. Hurray.

How can I convince my boss, and the higher ups, that A) This is a terrible idea, B) a better method/way of storing these