In this article, I'm sharing the story behind my first-ever paid bug bounty on HackerOne, where I uncovered a critical authorization vulnerability in a public program that led to the exposure of highly sensitive user data. This finding not only marked a major milestone in my bug bounty journey but also reinforced the importance of persistence, curiosity, and thinking beyond obvious attack paths.

The vulnerability stemmed from a broken authorization mechanism on an order-related endpoint. While the application initially appeared to expose only limited, non-sensitive information, deeper testing revealed that authenticated users could access other users' complete order details simply by manipulating object identifiers in the URL. This resulted in the disclosure of sensitive personally identifiable information (PII), including names, phone numbers, addresses, and even payment-related details.

What made this issue particularly severe was its simplicity. There was no need for complex exploitation techniques, privilege escalation, or advanced tooling. The server only verified whether a user was logged in, completely failing to enforce proper authorization checks to ensure that users could access only their own data. This classic case of Broken Object Level Authorization (BOLA / IDOR) significantly increased the real-world impact of the vulnerability.

In this article, you'll learn:

  • How OSINT and archived endpoints played a key role in discovering a hidden attack surface
  • Why seemingly low-impact endpoints can turn critical when tested in the right context
  • How improper authorization checks led to full user data exposure
  • The process of responsibly reporting the issue on HackerOne
  • Lessons learned after hundreds of informative and duplicate reports before landing a first bounty

Let's dive into how this vulnerability was discovered, the mindset behind the testing approach, and how persistence finally paid off with a $1000 HackerOne bounty.

A Quick Introduction

Before diving into the vulnerability details, here's a brief introduction about who I am.

My name is Mohaseen, and I'm a Cybersecurity Researcher and Bug Bounty Hunter with a strong focus on Web Application Security, Cloud Security, and Web3 security. I began my journey in ethical hacking and bug bounty hunting in 2019, and since then, I've been continuously learning, experimenting, and refining my skills through hands-on, real-world security testing.

Over the years, my vulnerability research and responsible disclosures have earned me multiple acknowledgments, including:

  • 4× Apple Hall of Fame
  • Recognition from several leading global organisation's
  • Industry-recognized certifications such as BSCP, eWPTX, eJPT, CRTA, CCSP-AWS, and more

Cybersecurity is more than just a profession for me.it's something I'm genuinely passionate about. I enjoy identifying security flaws that are often overlooked and working with organizations to help secure critical systems and protect sensitive user data.

The Bug -How It All Began

Every bug bounty hunter remembers their first real win. For me, this one didn't come from luck or some advanced exploit. it came from patience, curiosity, and thinking just one step beyond what was visible.

At that time, a close friend of mine from Pakistan and I were actively hunting on HackerOne public programs. Day after day, we were reporting issues, only to see the same outcomes again and again: informative, not applicable, or duplicate. While it was frustrating, we knew this phase was part of the journey. Each report, even the rejected ones, was sharpening our mindset.

One day, we decided to change our approach. Instead of jumping between multiple programs, we chose to commit fully to a single target (let's call it redacted.com). Our plan was simple but disciplined: spend an entire month on deep reconnaissance, understanding the application's behavior, and looking for subtle flaws others might overlook.

During the first week, I focused heavily on reconnaissance and OSINT. Along with common recon techniques, I started exploring archived endpoints URLs that had been indexed by crawlers, search engines, and web archive services over time. These old endpoints often tell stories about how an application evolved, and sometimes, they reveal things that were never meant to stay public.

As I was going through the archived URLs, most of them were predictable or irrelevant. But then, one particular pattern caught my attention: an endpoint resembling something like /order-details/<order_id>.

order id was something long text we cant predict it.

Out of curiosity, I opened a few of these URLs directly in the browser. The response was underwhelming at first. It only showed basic order information, such as product names and prices. No personal details, no payment data nothing that felt impactful enough to report. I almost moved on.

But something didn't sit right with me.

Instead of closing the tab, I paused and asked myself a simple question: "How does this endpoint behave when accessed by a logged-in user?"

So I logged into my account and revisited the same endpoint.

That's when everything changed.

Suddenly, the response expanded. Along with order details, the application revealed highly sensitive user information full name, shipping address, phone number, email address, and even card-related details. At that moment, it became clear that the application was performing authentication without proper authorization. The server was only checking whether a user was logged in or not which user was allowed to access that specific order.

In simple terms: any authenticated user could access anyone else's order details by modifying the order ID in the URL.

I tested this carefully with multiple requests to confirm the impact, ensuring everything was reproducible and well-documented. Once I was confident, I prepared a clean, detailed proof of concept and submitted the report through HackerOne, clearly explaining the broken access control issue and its real-world impact.

About a week later, something happened that I'll never forget.

Early in the morning, I woke up and casually checked my phone. There it was a notification from HackerOne. The report had been accepted, marked as high impact, and a $1,000 bounty had been awarded.

For a few minutes, I just stared at the screen.

This wasn't just about the money. It was validation. After nearly 200–250 informative and duplicate reports, this was my first confirmed bounty and it hit a major milestone straight away.

That moment reinforced a lesson I still carry today: persistence beats talent, and curiosity beats tools.

The Lesson

This experience reinforced a crucial lesson in bug bounty hunting and real-world security testing: impactful vulnerabilities are often the result of simple logic and authorization flaws rather than complex exploitation techniques. A single missing authorization check was enough to expose highly sensitive user data, highlighting how small oversights can lead to serious security risks.

The journey to this finding was not instant. It came after months of learning, hundreds of duplicate and informational reports, and continuous experimentation. This vulnerability became my first rewarded submission on a public HackerOne program, marking a significant milestone in my bug bounty journey.

More importantly, it reaffirmed that persistence, curiosity, and a methodical testing approach are key to success. Every unsuccessful report contributes to experience, and eventually, one well-understood vulnerability can make all the effort worthwhile.

I hope you enjoyed the article! I'm open to collaboration if you'd like to team up on bug bounty research or security projects, feel free to reach out.

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