This is my bank, what should my next steps be? Change my password/PIN? Withdraw my savings (temporarily)?
I guess management instructed them to do this.
I would advise against changing banks over this though. Knowing banks, this is not going to be the only one or even remotely the most serious security bug they ignored. And their competition is just not going to be better. The way security works at banks is threefold : (a) screw inattentive customers (b) watch backend systems for transactions like a hawk (c) call the police over every small problem claiming (correctly) that the financial system could fail if they don't track the culprits down for their current problem.
(For those that dont know, the bank's slogan used to be "Which bank? The Commonwealth Bank."