A Top Hunter’s Approach: Inside the Mind of @xiridium
For Cybersecurity Awareness Month, the GitHub Security Bug Bounty team is spotlighting one of its standout researchers: @xiridium. Known for uncovering complex business logic flaws and providing exceptionally clear reproduction steps, @xiridium has become a key figure in the program’s success. Their submissions not only surface nuanced vulnerabilities but also streamline triage, saving time for both researchers and engineers.
We sat down with @xiridium to discuss their entry into security research, their daily workflows, and the mindset that has led them to find some of the most impactful bugs in the GitHub ecosystem.
From CTFs to Real-World Targets
@xiridium’s journey began with capture the flag (CTF) competitions, where the idea of finding bugs in live applications seemed like a distant dream. “It was my dream to get my first bounty,” they recall. The prospect of joining the ranks of researchers who help fix real-world threats was a powerful motivator. What keeps them coming back, however, is twofold: the sense of professional validation from the community and the constant sharpening of technical skills.
When not hunting for vulnerabilities, @xiridium pursues a different kind of challenge: music. “At the age of 30, I started playing music and learning how to sing,” they say, noting that it helps switch context away from work. And yes, a fair share of bounty earnings goes toward Lego.
Learning on Demand, Not by Rote
Keeping up with the rapidly shifting vulnerability landscape is a deliberate process for @xiridium. Rather than following trends reactively, they learn on demand. “Whenever I see some protobuf code looking interesting or a new cloud provider is used, that is the moment when I say to myself, ‘Ok, now it’s time to learn about this technology,’” they explain.
They recommend following accounts like Intigriti on X for leads, but with a caveat: “Don’t blindly use all the tips you see. They help, but only when you understand where they come from. Running some crazily clever one-liner rarely grants success.”
The Tools That Change the Game
For @xiridium, large language models (LLMs) have been transformative. Their advice for using them effectively mirrors delegation: “Think of an LLM as though it is a junior developer that was assigned to you. The junior knows how to code, but is having hard times tackling bigger tasks. So always split tasks into smaller ones, approve ChatGPT’s plan, and then let it code.” This approach proves useful for scripting, credential verification, and getting a quick overview of new technologies.
Diving Deep Over Going Wide
Rather than scanning many targets, @xiridium prefers to immerse themselves in a single application. The goal is to understand it so thoroughly that they could theoretically rebuild it. Their milestone: “Okay, I know every endpoint and request parameter good enough.” At that point, they shift focus to the highest-impact areas and revisit the program’s scope.
This deep-dive method often uncovers architectural anomalies that hint at underlying issues. For example, finding two endpoints for the same data, like /user and /data/users, raises a red flag. “Why would there be two different things for the same data?” The answer, they note, is often that two teams didn’t sync, leading to ambiguity and complexity—prime conditions for bugs. Similarly, spotting a GCP-hosted subdomain among nine AWS-hosted ones signals different management teams and a higher probability of flaws.
Favorite Bug Classes: Credentials and Logic
@xiridium’s specialty lies in leaked credentials and intricate business logic. They advise hunting for unique endpoints during deep dives, and suggest leveraging GitHub search or Google dorks on platforms like Slideshare, Postman, and Figma to map out developer workflows. While these findings rarely yield direct vulnerabilities, they are instrumental in understanding how an application operates behind the scenes.
Advice for Aspiring Researchers
For those starting out, @xiridium points to PortSwigger Labs and Hacker101 as foundational resources. Their suggestion: work through the easiest tasks in each category, identify what captivates you, then go all in—reading reports, solving CTFs, and tackling labs related to that bug class.
One hard-won lesson they wish they had known sooner: “Forget about ‘Definitely this is not vulnerable’ or ‘I am sure this asset was checked enough.’” They’ve repeatedly seen hackers find bugs on the www domain of public programs that others had dismissed. And when you have knowledge of a rare vulnerability class, they recommend testing for it everywhere—they once found Oracle padding in an authentication cookie and have since looked for it on every target they encounter.
