The Zero-Day Deduction

2 AM. The screen burned my retinas. Coffee was a memory. The tax-portal.io bug bounty program was a bust. Nothing. Just another dead end in a long line of dead ends. I was ready to quit. Close the laptop. Sleep.

One last look at the proxy logs.

A flicker in the traffic history. A standard GET request to fetch a user's documents. My own, from my test account. The URL was clean, but the parameter caught my eye. user_id=1054.

An Insecure Direct Object Reference. An IDOR. The simplest, most devastating bug in the book. It couldn't be. Not on a financial platform.

Muscle memory took over. I sent the request to the repeater tool. The original user_id=1054 was there. My finger hovered over the '4'. Click. Backspace. '5'.

user_id=1055.

Parameter tampering. I forwarded the request. I expected a 403 Forbidden. An error message. A wall.

The server didn't say no.

http

GET /api/v1/tax-documents/view?id=1055 HTTP/1.1
Host: secure.tax-portal.io
Cookie: session=eyJh... (My Session)

// RESPONSE (200 OK)
{
  "status": "success",
  "data": {
    "full_name": "Sarah Jenkins",
    "ssn": "***-**-8921",
    "adjusted_gross_income": 85000,
    "refund_status": "PENDING"
  }
}

My blood went cold. Sarah Jenkins. A real person. Her PII, sitting right there on my screen. Her Social Security Number. Her income. All of it. Returned with a cheerful 200 OK.

This wasn't a bug. It was a hemorrhage.

My hands flew. A few lines of Python. A simple loop. for user_id in range(1, 4000000):. I ran the script.

My terminal flooded with 200 OK. Thousands of them per second. The entire user database. Four million people. Their financial lives, their identities, all exposed to the public internet by a single, broken line of code.

I killed the script. The silence in the room was deafening. I had it all. I could download everything. I could burn the company to the ground with a single anonymous post. The power was absolute. Intoxicating.

I stared at the screen. At Sarah Jenkins' life, reduced to a JSON object.

I opened a new text file. My fingers found the keyboard.

Title: Critical IDOR Vulnerability in tax-portal.io Leading to Full PII Exposure.

The bounty didn't matter. This was about responsible disclosure. This was about fixing the hole before someone else found it. Someone who wouldn't be so kind.