API Security Hardening After a Near-Miss Breach
Led an emergency API security sprint after a penetration test revealed 12 critical vulnerabilities across public-facing APIs. All vulnerabilities resolved in 3 weeks with a clean follow-up pen test.
Challenge
Penetration test revealed 12 critical vulnerabilities across public-facing APIs including broken authentication and injection risks, putting customer data at immediate risk.
Solution
Led an API security sprint — OWASP Top 10 remediation, rate limiting, input validation overhaul, and API gateway deployment with WAF integration.
Result
All 12 critical vulnerabilities resolved in 3 weeks, follow-up penetration test passed clean with zero critical or high findings.
The Problem
I was managing the delivery programme for a global enterprise's customer-facing platform when a routine third-party penetration test delivered alarming results. The report identified 12 critical vulnerabilities across our public-facing APIs — broken authentication on two endpoints, SQL injection vectors on three others, excessive data exposure on several responses, and missing rate limiting across the board. Two of the findings were rated as immediately exploitable.
This was not a theoretical risk. The APIs served a mobile application with over 500,000 active users and processed payment-adjacent data. The CISO escalated the findings to the executive team, and I was asked to lead the remediation effort as an emergency priority. We had a hard deadline: the client's compliance team required a clean re-test within 30 days.
What I Did
I stood up a dedicated security sprint within 48 hours. I pulled four senior engineers from their current work, brought in the security team as embedded reviewers, and structured the three-week effort around the OWASP Top 10 as our remediation framework.
The first week focused on the two immediately exploitable vulnerabilities — the broken authentication endpoints. We implemented proper token validation, added session management controls, and enforced authentication consistently across all API routes. Every fix went through a security-focused code review before merging.
The second week addressed injection risks and data exposure. We overhauled input validation across all endpoints, implementing parameterised queries where raw SQL had been used, and added strict schema validation on all request payloads. For excessive data exposure, we restructured API responses to return only the fields the consuming application actually needed, rather than dumping entire database objects.
The third week was dedicated to infrastructure-level hardening. We deployed an API gateway with Web Application Firewall integration, implemented rate limiting and throttling policies, added request logging and anomaly detection, and established automated security scanning in the CI/CD pipeline so these issues would be caught before reaching production in the future.
Throughout the sprint, I maintained a daily risk dashboard visible to the CISO and executive sponsors, tracking each vulnerability from open to remediated to verified.
The Outcome
All 12 critical vulnerabilities were resolved within the three-week window. The follow-up penetration test came back clean — zero critical or high findings. The API gateway and WAF we deployed blocked over 2,000 malicious requests in its first month of operation, validating the infrastructure investment. The automated security scanning integration into CI/CD has since caught 15 vulnerabilities in pull requests before they reached any environment. What started as a crisis became the catalyst for a permanent security-first engineering culture.