Exploiting a Vulnerable Developer API
This blog details my journey of uncovering a series of vulnerabilties in a hardened system
The Hidden Proxy
Some time ago, I was invited to security-test a private application. Although the main platform was robust, having been vetted by top hackers, I decided to examine its developer interface.
Most modern applications offer a developer API for programmatic access and integration. In this case, the main application operated on app.example.com, while the developer API resided on app.example.io. Heuristic analysis revealed that the developer domain was essentially a proxy or wrapper for the main application’s backend.
While the main app was well-secured, the developer API showed interesting behaviour. By utilising specific headers discovered in the site’s JavaScript files, I was able to bypass existing security controls. This revealed significant flaws, including IDORs and privilege escalation vulnerabilities. Through these, I was able to access sensitive logs and data belonging to other organisations.
To most this might not contain new novel techniques but reinforces that simple issues are still very prevalent in the World Wide Web.
Generic automated checks would have definitely missed such issues as one needed some deeper knowledge on the application.