When a form is submitted, if sensistive data such as a checking account number, routing number, SSN, etc is showing up in the 'Submission Data' section of a customer's record as in the example image below...
...then you just need to change the Submission Data field type for that form field from a 'Form' type into a 'DB' type.
Head to the Admin Portal (back end) of your instance (add /a to the end of your instance URL to get to your Admin Portal), and click Config:
Next, navigate to the Submission Data tab and click on the Person Data Layout 'Click Here to Edit' button:
Scroll down the Person Data Layout list until you find the form field that is appearing in Submisson Data but should not be. It will probably be set to a 'FORM' type. Change this type to 'DB':
Click Done at the bottom of the Person Data Layout list, then click Save to save your configuration changes. You can submit a test form to double-check that the applicable data is no longer showing in a person's Submission Data.