API Security: Common Vulnerabilities and How to Fix Them

APIs are the backbone of modern applications but they are also prime targets for attackers. The OWASP API Security Top 10 identifies the most critical API risks. Understanding and addressing these vulnerabilities is essential for secure application development.

Weak authentication mechanisms allow attackers to assume identities. Vulnerabilities include weak passwords missing MFA predictable tokens and no rate limiting. Solutions include implementing OAuth 2.0 OpenID Connect enforcing strong password policies using MFA implementing rate limiting and account lockout.

Attackers manipulate object IDs to access unauthorized data. Example vulnerability GET api users 123 returns any users data. Solutions include implementing proper authorization checks on every endpoint using random unpredictable IDs validating user permissions server-side never trusting client-supplied IDs without verification.

APIs returning more data than needed expose sensitive information. Vulnerability example returning full user objects including passwords and tokens. Solutions include implementing proper response filtering using DTOs Data Transfer Objects returning only necessary fields avoiding generic serialize-everything approaches.