API security starts with knowing which APIs exist, who can call them, and what data they expose.
Check authentication and authorization separately: a valid identity should not automatically access every object or action
Validate input, limit sensitive response fields, protect secrets, apply appropriate rate limits, and log security-relevant events without recording unnecessary sensitive data
Test business logic as well as common technical weaknesses
Include APIs in change reviews and incident plans, and define ownership for remediation
Use testing only against systems you own or are explicitly authorized to assess.
This article provides general educational information, not legal, compliance, or security assurance. The appropriate steps depend on your environment and requirements.