Business logic refers to the custom rules, workflows, and processes that define how an application handles its core operations. In an e-commerce application, business logic includes pricing calculations, discount rules, inventory management, and checkout flows. In a banking application, it encompasses transfer limits, account validation, and transaction processing rules. Business logic vulnerabilities arise when these rules can be manipulated to produce outcomes the developers did not intend.
How It Works
Business logic is implemented as the layer between the user interface and the database, encoding the specific rules that make each application unique. Unlike generic security controls such as input validation or authentication, business logic is specific to each application's purpose and domain. This specificity means that business logic vulnerabilities are unique to each application and cannot be detected by generic vulnerability scanners.
Business logic flaws occur when an attacker manipulates the intended workflow to achieve an unauthorized outcome. Examples include applying a discount code multiple times to reduce a price below zero, skipping mandatory verification steps by directly accessing later stages of a process, manipulating quantities or prices in a shopping cart by modifying client-side values, or exploiting race conditions to use a single-use voucher multiple times.
These vulnerabilities are particularly subtle because each individual step in the exploited flow may appear to function correctly in isolation. The flaw exists in the relationship between steps, the order of operations, or the assumptions made about user behavior. Automated security scanners cannot detect these issues because they require understanding the application's intended behavior and business rules to recognize when those rules are being violated.
Why It Matters
Business logic vulnerabilities often have the highest real-world impact because they directly affect financial transactions, user permissions, or data integrity. Security assessments that focus only on technical vulnerabilities like injection or XSS miss these critical flaws. Effective testing requires understanding the application's business domain and systematically testing whether its rules can be circumvented, manipulated, or abused.
Need your application tested? Get in touch.