My bank considers transactions done using login credentials to be final. There is no recourse if someone steals your money.
Last year an iOS mail application called "Spark" (otherwise a great app) decided to quietly upload my login and password to their cloud servers so that their servers can access my mail for me. I dropped the app immediately (https://jan.rychter.com/enblog/spark-email-app-why-i-dont-us...).
This should not be considered acceptable. If you want to let users authorize external access to account data, use Oauth2.