It's nearly as secure as going to the ATM to deposit the check and most banks are OK with the increased risk because they have extra identifiers (phone/app info) when you 'scan' the check. Which is to say the whole process is not terribly secure.
History wise it came about with the removal (or reduction) of check float when checks began to be processed electronically (turned into an ACH transaction with images of front & back being taken by the submitting bank). In the last TOS I read about check scanning what is actually happening is that your scanning of the check replaces the bank's scanning and they are using extracted data to create the ACH transaction. In the meantime they extend credit to you to match the amount they would normally advance you (varies by account and amount). It's been a while but I recall it being specifically credit as opposed to the usual 'available funds' at an ATM; this seems a distinction without a difference.
In the end - it's not secure or at least not much less secure than going to an ATM to deposit the check. The difference is that the ATM keeps the physical check for some small period of time such that if there is a problem with the ACH the bank might have physical possession of the check to assist in a fraud investigation (not that I think they'd need it as the law enabling electronic clearance I believe made the electronic images equivalent in all ways to the physical check).
History wise it came about with the removal (or reduction) of check float when checks began to be processed electronically (turned into an ACH transaction with images of front & back being taken by the submitting bank). In the last TOS I read about check scanning what is actually happening is that your scanning of the check replaces the bank's scanning and they are using extracted data to create the ACH transaction. In the meantime they extend credit to you to match the amount they would normally advance you (varies by account and amount). It's been a while but I recall it being specifically credit as opposed to the usual 'available funds' at an ATM; this seems a distinction without a difference.
In the end - it's not secure or at least not much less secure than going to an ATM to deposit the check. The difference is that the ATM keeps the physical check for some small period of time such that if there is a problem with the ACH the bank might have physical possession of the check to assist in a fraud investigation (not that I think they'd need it as the law enabling electronic clearance I believe made the electronic images equivalent in all ways to the physical check).