Thank you for posting here in QuickBooks Community. I'll provide information on how your Online Banking secure through QuickBooks.
Protecting the privacy and security of your financial information is our top priority. Intuit software products, including QuickBooks Online, protect your transactions with multiple layers of security so you can bank online with confidence. The connection for online banking is always "read-only" so that no one can use any of your information in our product to move any money. In addition, we don’t sell, rent, or share your information with third parties for their promotional use.
To ensure that only the intended audience can read a message or access data, we combine Secure Sockets Layer (SSL) protocol and RSA Security Inc. encryption to provide message encryption when communicating online to maximize the security of your data. QuickBooks Online provides a password feature to ensure that only people with the correct password have access to your financial information. That said, I'd suggest making sure that your accountant doesn't know your bank login credentials.