Business Logic Vulnerabilities

Business Logic Vulnerabilities

Business logic vulnerabilities represent a special class of design flaws where the application correctly implements insecure requirements. Consider an online store that allows customers to apply multiple discount codes. If the business logic doesn't account for negative-value items combined with percentage discounts, customers might receive money back while "purchasing" products. This isn't a coding bug—the system works exactly as designed. The design itself contains the vulnerability.

These vulnerabilities often emerge from incomplete threat modeling or failure to consider edge cases. A financial application might allow users to transfer money to themselves, not anticipating that concurrent transfers could exploit race conditions to duplicate funds. A voting system might prevent double-voting from the same account but not consider that users could create multiple accounts. These scenarios highlight why security must be considered during design, not added as an afterthought.