SourceCodester Loan Management Business Logic

SourceCodester Loan Management System v1.0 allows authenticated administrators to submit negative penalty rates for loan overdue payments by bypassing client-side validation through direct HTTP POST manipulation, enabling financial fraud through reversed penalty calculations that benefit borrowers instead of lenders. The vulnerability requires authenticated access but no CVSS score, EPSS probability, or formal patch status is available; however, publicly available exploit code confirms the vulnerability's technical feasibility.

SourceCodester Loan Management System v1.0 accepts negative integer values for loan plan duration due to insufficient input validation on the months parameter, allowing attackers to create loan plans with invalid negative durations that may cause unexpected system behavior or financial miscalculations. Publicly available exploit code exists, though real-world impact depends on downstream business logic that consumes these invalid loan plans.