Log into the bank and click the "log out of all sessions" to invalidate all cookies. Or if an attacker changed your credentials walk into the back and have a b

Log into the bank and click the "log out of all sessions" to invalidate all cookies. Or if an attacker changed your credentials walk into the back and have a banker do it and then have the show/reverse all changes and transactions the attacker made. If the option does not exist, demand they add it or you and your money will go to another bank. Not all websites have this option but they would if enough customers demanded it.