I remember, many years ago, a story of someone who took a whole pile of blank deposit slips from the banks, and MICR encoded his account number along the bottom

I remember, many years ago, a story of someone who took a whole pile of blank deposit slips from the banks, and MICR encoded his account number along the bottom - when customers came in to make a deposit and the slip was scanned electronically, anything handwritten by the customer was over-ridden by the pre-printed account number - don't know how much they got away with, but clever none-the-less. If there is something to be exploited somewhere, someone will find it.