February 3, 2026

My First Week: 3 Business Logic Bugs in Major E-Commerce 🛒🐛

: Hunting for Broken Logic 🕵️‍♂️

Ali Alassaf

2 min read

Last week, I decided to start my journey in Bug Bounty hunting. Instead of looking for complex code vulnerabilities (like RCE or SQLi), I decided to focus on something that requires human thinking: Business Logic Errors 🧠.

I chose a target – a large European e-commerce website (let's call it "Target-X" 🇪🇺) – and fired up Burp Suite 🛠️. I wanted to see if I could break the rules set by the developers.

To my surprise, within just one week, I found three different vulnerabilities where I successfully bypassed the site's restrictions. Here is the story of what I found. 👇

Bug #1: Bypassing the Minimum Order Value 🔓

The Rule: 🛑

The website has a strict rule: You cannot checkout if your cart total is less than $50. The "Checkout" button is greyed out (disabled) in the browser.

The Hack: ⚡

I asked myself: "Is this restriction enforced by the server, or is it just the frontend interface blocking me?"

  • I added a cheap pair of socks ($5) to my cart 🧦.

  • The "Checkout" button was disabled 🚫.

  • I manually typed the checkout URL into my browser address bar: site.com/checkout/payment.

The Result: ✅

The server did not check the cart total! The payment page opened successfully. It asked for my credit card details for a $5 order, completely ignoring the $50 rule 💳.

Bug #2: The Shipping Fee Trick 🚚

The Rule: 📦

Free shipping is only available for large orders. Small orders must pay a shipping fee.

The Hack: 🔄

I used a technique called "Forced Browsing".

  • I repeated the steps from the first bug (forcing my way to the payment page with a cheap item).

  • Because I skipped the normal steps (address selection -> shipping method -> payment), the system got confused 😵‍💫.

  • The backend logic failed to apply the shipping fee at that specific stage.

The Result: 💸

I was at the final payment screen with a cheap item and $0 shipping cost, which should have been impossible for a small order.

Bug #3: Exploiting Promo Codes 🏷️

The Rule: 📜

There was a coupon code that worked on a condition: "Get 20% off if you buy Item A AND Item B together."

The Hack: ✂️

  • I added both Item A and Item B to my cart to activate the discount.

  • I went to the checkout page.

  • I intercepted the checkout request using Burp Suite.

  • I modified the request to remove "Item B" from the cart just milliseconds before the server processed it.

The Result: 🎉

The server processed the order for "Item A" only, but it forgot to remove the discount. I effectively got the discount on a single item without meeting the condition.

The Outcome: A Hard Lesson 📉

I wrote professional reports for all three vulnerabilities and submitted them to the platform. I was confident because I had clearly broken the site's logic multiple times.

The security team reviewed my reports, and the final decision for all three was:

"Status: Informative" ℹ️ (Closed without bounty).

Why? 🤔

The response was fair but tough:

"You successfully bypassed the UI, but you did not prove the final financial impact. The backend payment system might reject the order after you click 'Pay', or the warehouse system might flag it later."

Conclusion: What I Learned 🎓

Even though I didn't earn money last week, I earned experience.

  • Logic is Weak: Developers often trust the frontend too much 💻.

  • Impact is Everything: Next time, I won't stop at the payment page. I need to find a safe way to prove that the company actually loses money (Impact) to get the report accepted 💰.

It was a great start to my bug bounty journey.

#BugBounty #CyberSecurity #BusinessLogic #Writeup #Infosec #Learning