Security belongs in every release, not at the end.

Start with what needs protecting

Map the information the application handles, who needs access, and what could go wrong. Consider disclosure, unauthorized changes, unavailable services, and abuse of legitimate features.

This does not need to begin as a large document. A short threat discussion around the most important user journeys can expose assumptions before they become expensive to change.

Treat authorization as a product rule

Signing in identifies a user. It does not establish what that user is allowed to do. Define permissions around real roles and enforce them on the server for every protected action.

• Can one customer access another customer's records?
• Can a user change their own role or approval limits?
• Are sensitive exports controlled and logged?
• Does removing access invalidate active sessions as required?
• Are administrative actions visible to the right reviewers?

Make safe handling the default

Validate untrusted inputs, encode outputs appropriately, protect secrets, and keep sensitive data out of unnecessary logs. Use established libraries and platform features rather than designing custom authentication or cryptography.

Review dependencies and update them through a controlled process. Automated scanning can identify known issues, but it does not replace reviewing how the application uses a component.

Plan to detect and recover

Agree the signals that indicate abuse or failure and the people who will respond. Make sure alerts are actionable, access is available during an incident, and communications are planned.

Security requirements vary by sector and jurisdiction. A practical engineering baseline is not a compliance certification. Get qualified specialist advice where a contractual, regulatory, or high-risk requirement applies.