---
title: "Discussion on \"Change One Number. Take Everything.\" | Hashnode"
description: "Discussion on \"Change One Number. Take Everything.\". The #1 Web Vulnerability | Why 94% of Applications Fail This Test"
url: "https://hashnode.com/posts/change-one-number-take-everything/6a7afaf6beeabc2bbd49a950"
---

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# [Change One Number. Take Everything.](https://blog.ahmershah.dev/change-one-number-take-everything?utm_source=hashnode&utm_medium=feed)

The #1 Web Vulnerability | Why 94% of Applications Fail This Test

Aug 11 · 21 min read · blog.ahmershah.dev  
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## Written by

[Syed Ahmer Shah](https://hashnode.com/@syedahmershah)

@syedahmershah · Hyderabad, Pakistan

  
[View profile](https://hashnode.com/@syedahmershah)

Hey, I’m Syed Ahmer Shah — a full-stack dev & software engineering student building cool stuff. I write about web dev and the lessons I learn along the way.

I’m Syed Ahmer Shah — a full-stack developer and Software Engineering student focused on building, learning, and understanding how software comes together. I share what I learn through technical writing, development notes, and project case studies, covering code, AI, problem-solving, challenges, and the developer journey.

## Responses 11

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[Legend Spaw](https://hashnode.com/@arhumshahdev)

[Aug 12](https://hashnode.com/posts/change-one-number-take-everything/6a7afaf6beeabc2bbd49a950/comment/6a7c0f9a9f9ff4f2a120f11e)

Informative

[Keshav](https://hashnode.com/@keshavdev2)

[Aug 11](https://hashnode.com/posts/change-one-number-take-everything/6a7afaf6beeabc2bbd49a950/comment/6a7b4b2938da7962df543c58)

This is a great reminder that serious security issues don't always require sophisticated exploits. Sometimes a simple logic gap can have a much bigger impact.

[Keshav](https://hashnode.com/@keshavdev2)

[Aug 11](https://hashnode.com/posts/change-one-number-take-everything/6a7afaf6beeabc2bbd49a950/comment/6a7b4b1d497f25a183a28567)

The vulnerable vs. fixed code example makes the issue very practical. Sometimes seeing the missing condition in the query is all it takes for the concept to click.

[ObscuraLang](https://hashnode.com/@farzeenshahdev)

[Aug 11](https://hashnode.com/posts/change-one-number-take-everything/6a7afaf6beeabc2bbd49a950/comment/6a7b4aa6474ef320393560c0)

I like the point about UUIDs not being a replacement for authorization. Making IDs unpredictable helps with enumeration, but it doesn't solve the actual access-control problem.

[ObscuraLang](https://hashnode.com/@farzeenshahdev)

[Aug 11](https://hashnode.com/posts/change-one-number-take-everything/6a7afaf6beeabc2bbd49a950/comment/6a7b4a84474ef32039355fcd)

Really good explanation of the difference between authentication and authorization. That distinction is easy to overlook when focusing mainly on getting the login flow right.

[Aley Reza](https://hashnode.com/@farzeenshah)

[Aug 11](https://hashnode.com/posts/change-one-number-take-everything/6a7afaf6beeabc2bbd49a950/comment/6a7b49b17302f890af4459ce)

The biggest takeaway for me is that authorization needs to be treated as part of the architecture, not something developers remember to add to individual endpoints.

[Aley Reza](https://hashnode.com/@farzeenshah)

[Aug 11](https://hashnode.com/posts/change-one-number-take-everything/6a7afaf6beeabc2bbd49a950/comment/6a7b499f7302f890af445881)

The hotel key-card analogy makes IDOR much easier to understand. It really shows how authentication alone doesn't mean a user should have access to every resource.

[My Creations](https://hashnode.com/@manjotsingh)

[Aug 11](https://hashnode.com/posts/change-one-number-take-everything/6a7afaf6beeabc2bbd49a950/comment/6a7b0e5ee0e48862f8469289)

The point about authorization being enforced structurally really stood out to me.

[Atef Kurusan](https://hashnode.com/@atefkurusan)

[Aug 11](https://hashnode.com/posts/change-one-number-take-everything/6a7afaf6beeabc2bbd49a950/comment/6a7b0d3fcc1a0dffbf349136)

The hotel key-card analogy makes IDOR incredibly easy to understand.

[Mustafa](https://hashnode.com/@mustafaalid)

[Aug 11](https://hashnode.com/posts/change-one-number-take-everything/6a7afaf6beeabc2bbd49a950/comment/6a7b0ccef38c200be8e81218)

Changing one number shouldn't expose another user's data. Great breakdown of IDOR.

[Sahil](https://hashnode.com/@sahilkumardev)

[Aug 11](https://hashnode.com/posts/change-one-number-take-everything/6a7afaf6beeabc2bbd49a950/comment/6a7b096d5fa9ded32535ffcb)

This is a great reminder that security flaws don't always need sophisticated exploits.