Anyone remember CDNow? They rewarded referral purchases with $5 gift certificates. But they awarded the gift certificates before the referral purchase cleared. At the time, you could also trivially acquire a "valid" unique Mastercard number using $0-balance "Web Certificates". Long story short, you could write a script that would generate an unbounded credit for yourself at CDNow. People raped them with it.
Problems like this were really common in the late '90s. They persist today, but are more subtle. We always test for $-1.00 input flaws, and they aren't frequent.
The people who are actively exploiting these can give you any number of rationalizations for how legal their actions are, but at the end of the day what's protecting them is that they're staying below the noise floor for civil and criminal attention. It's still just fraud.
Problems like this were really common in the late '90s. They persist today, but are more subtle. We always test for $-1.00 input flaws, and they aren't frequent.
The people who are actively exploiting these can give you any number of rationalizations for how legal their actions are, but at the end of the day what's protecting them is that they're staying below the noise floor for civil and criminal attention. It's still just fraud.