When Banking APIs Become a Financial Security Weak Point

Banking APIs enable financial institutions, payment providers, and authorized third-party applications to exchange information and perform defined financial operations. However, secure communication and successful authentication do not necessarily establish that every requested action is authorized. This research examines how weaknesses in API authentication, object-level authorization, access-token controls, and transaction permissions can create security risks across interconnected financial systems.

Drawing on the OWASP API Security Top 10, the OpenID Foundation's Financial-grade API 2.0 Security Profile, and European banking regulatory evidence, the study distinguishes recognized technical vulnerabilities from confirmed exploitation and broader payment fraud. It examines the relationship between verified identity, authorized access, transaction context, and the financial operation performed, while emphasizing the evidence required before attributing financial losses to API security failures.