This repository is a demo fintech application, not a production payment processor.

• Removed client-controlled authentication cookies.
• Removed the exposed exchange-rate API credential.
• Added server-side sessions with secure cookie flags.
• Added CSRF validation for authentication and transfer actions.
• Added generic login errors to reduce account enumeration.
• Added server-side validation for transfer recipients and amounts.
• Made balance debits atomic and wrapped transfers in a database transaction.
• Escaped transaction/user output rendered into HTML.
• Added database indexes for transaction history.
• Moved database credentials to environment variables.
• Added web-server protection for application/configuration directories.

• MFA and device/session management.
• Rate limiting and bot protection.
• Idempotency keys for transfer requests.
• A proper double-entry ledger instead of directly mutating balances.
• Immutable audit logs and reconciliation.
• Fraud/AML/KYC controls where applicable.
• Payment provider/webhook verification.
• Exchange-rate caching, freshness checks, and provider failover.
• Automated tests, CI, static analysis, dependency auditing, and monitoring.