This is 3D Secure — an extra bank-side identity check some businesses have enabled for every new card. If it's on, after you submit your card details you may be redirected to confirm the setup with your bank before the card is fully saved; you'll see a success or failure message and be returned to your profile a few seconds later either way. This is an internal switch Sprwt turns on for a business's Stripe processing — it isn't something you or the business can toggle from the regular account settings.