[upl-image-preview uuid=eb12b880-98af-46ae-8dbe-720ee99286a7 url=https://hacklivly.com/assets/files/2025-03-26/1742981121-167985-business-logic-flaws.png alt={Business Logic Flaws ?}] **Hey guys, Rocky here!** 🕵️♂️💡 Welcome to **Day 15** of the *Daily Web Hacking* series! Today, we’re tackling **Business Logic Flaws**—the sneaky vulnerabilities that let hackers break apps *without* exploiting code. Think of it as outsmarting the app’s *design* instead of its defenses. Ready to learn how a simple coupon can crash a business or a tweaked parameter can turn you into an admin? Let’s dive in! --- ### **What Are Business Logic Flaws?** These flaws abuse how an app is *meant* to work. No SQLi, no XSS—just pure manipulation of workflows. **Example**: An e-commerce app lets users apply coupons. If there’s no limit on usage: ```http POST /apply-coupon { "code": "FREEMONEY", "uses": 100 } ``` → Attacker claims $10,000 in discounts. **Why they’re dangerous**: * **Invisible to scanners**: Burp, Nessus, and ZAP won’t catch them. * **High impact**: Financial fraud, data leaks, account takeovers. * **Hard to fix**: Requires redesigning features, not just patching code. --- ### **Types of Business Logic Flaws** #### **1. Authentication Bypass** * **The "Forgot Password" Trap**: ```http POST /reset-password { "email": "victim@company.com", "new_password": "Hacked123" } ``` *No email ownership check? Instant account takeover.* #### **2. Privilege Escalation** * **Hidden Parameter Tampering**: ```http POST /upgrade-account { "role": "admin" } # Originally "user" ``` #### **3. Workflow Hijacking** * **Skipping Payment in Checkout**: ```http Step 1: Add to cart → Step 3: Confirm order # Skip Step 2 (Payment) ``` #### **4. Race Conditions** * **Double-Spending Money**: ```bash # Send parallel requests curl -X POST /transfer?amount=100 & curl -X POST /transfer?amount=100 ``` *Balances update too slowly? Steal $200 instead of $100.* #### **5. Negative Quantity Exploits** * **E-Commerce "Refund" Hack**: ```http POST /cart { "product_id": "100", "quantity": -10 } # Get paid $1,000 instead of paying! ``` --- ### **Real-World Disasters** 1. **Uber’s $0 Rides (2016)**: Manipulating ride parameters for free trips. 2. **Twitter’s SMS Bypass (2022)**: Skipping SMS verification to hijack accounts. 3. **Crypto Exchange "Penny Attack"**: Buying Bitcoin for $0.01 via floating-point abuse. --- ### **Step-by-Step Exploitation: Free Premium Access** **Goal**: Upgrade to a "premium" plan without paying. 1. **Map the Upgrade Flow**: * Select plan → Enter payment details → Confirm. 2. **Intercept the Request**: ```http POST /upgrade-plan { "plan": "premium", "price": 99.99 } ``` 3. **Tamper with the Price**: ```http { "plan": "premium", "price": 0.01 } ``` 4. **Profit**: Server accepts $0.01 for a $99.99 plan. --- ### **Tools & Techniques** #### **1. Burp Suite** * **Repeater**: Test parameter tampering (e.g., `price`, `role`). * **Turbo Intruder**: Exploit race conditions with parallel requests. #### **2. Manual Testing** * Ask: *"What if I skip this step?"* or *"What if I input -1?"* #### **3. Threat Modeling** * Diagram workflows and brainstorm abuse cases *before coding*. --- ### **Defending Your App** #### **1. Server-Side Validation** * Never trust client-side checks: ```python # BAD: Client-side check if discount MAX_DISCOUNT: raise ValidationError("Nice try.") ``` #### **2. Stateful Workflows** * Track steps server-side: ```python session['checkout_step'] = 2 # Block skipping to step 3! ``` #### **3. Rate Limiting** * Block coupon spam, password resets, or balance transfers: ```nginx limit_req_zone $binary_remote_addr zone=coupon:10m rate=5r/m; ``` #### **4. Log & Alert** * Monitor anomalies: * Negative quantities. * 100 failed logins in 1 minute. --- ### **Why Developers Miss These Flaws** * **Focus on code, not design**: “It works” ≠ “It’s secure.” * **Assumption of honesty**: “Users won’t *abuse* this feature… right?” --- ### **Final Thoughts** Business logic flaws are the ultimate test of *thinking like a hacker*. They don’t require exploits—just creativity and a willingness to break the rules. To defend your app: * **Question every workflow**: “How can this be abused?” * **Test manually**: Scanners can’t catch design flaws. * **Embrace paranoia**: Assume users *will* find loopholes. **Up Next**: **Day 16: Security Misconfiguration – Defaults, Debug Modes, and Open Doors** --- **Rocky out!** ✌️ --- **P.S.** If you’re enjoying this series, share it with your team! Let’s turn *“It works”* into *“It’s secure.”* **Discussion Question**: What’s the craziest logic flaw you’ve seen? I once upgraded to “admin” by setting `plan_id` to `-1`. 😅 Spill your stories below! 👇

Web Hacking Series - Part 15: Business Logic Flaws🏦🔍🚀

rocky

{Business Logic Flaws ?}

Hey guys, Rocky here! 🕵️♂️💡

Welcome to Day 15 of the Daily Web Hacking series! Today, we’re tackling Business Logic Flaws—the sneaky vulnerabilities that let hackers break apps without exploiting code. Think of it as outsmarting the app’s design instead of its defenses. Ready to learn how a simple coupon can crash a business or a tweaked parameter can turn you into an admin? Let’s dive in!

—

What Are Business Logic Flaws?

These flaws abuse how an app is meant to work. No SQLi, no XSS—just pure manipulation of workflows.

Example:
An e-commerce app lets users apply coupons. If there’s no limit on usage:

POST /apply-coupon  
{ "code": "FREEMONEY", "uses": 100 }

→ Attacker claims $10,000 in discounts.

Why they’re dangerous:

Invisible to scanners: Burp, Nessus, and ZAP won’t catch them.
High impact: Financial fraud, data leaks, account takeovers.
Hard to fix: Requires redesigning features, not just patching code.

—

Types of Business Logic Flaws

1. Authentication Bypass

The “Forgot Password” Trap:

  POST /reset-password  
  { "email": "victim@company.com", "new_password": "Hacked123" }

No email ownership check? Instant account takeover.

2. Privilege Escalation

Hidden Parameter Tampering:

  POST /upgrade-account  
  { "role": "admin" }  # Originally "user"

3. Workflow Hijacking

Skipping Payment in Checkout:

  Step 1: Add to cart → Step 3: Confirm order  # Skip Step 2 (Payment)

4. Race Conditions

Double-Spending Money:

  # Send parallel requests  
  curl -X POST /transfer?amount=100 & curl -X POST /transfer?amount=100

Balances update too slowly? Steal $200 instead of $100.

5. Negative Quantity Exploits

E-Commerce “Refund” Hack:

  POST /cart  
  { "product_id": "100", "quantity": -10 }  # Get paid $1,000 instead of paying!

—

Real-World Disasters

Uber’s $0 Rides (2016): Manipulating ride parameters for free trips.
Twitter’s SMS Bypass (2022): Skipping SMS verification to hijack accounts.
Crypto Exchange “Penny Attack”: Buying Bitcoin for $0.01 via floating-point abuse.

—

Step-by-Step Exploitation: Free Premium Access

Goal: Upgrade to a “premium” plan without paying.

Map the Upgrade Flow:
- Select plan → Enter payment details → Confirm.

Intercept the Request:

   POST /upgrade-plan  
   { "plan": "premium", "price": 99.99 }

Tamper with the Price:

   { "plan": "premium", "price": 0.01 }

Profit: Server accepts $0.01 for a $99.99 plan.

—

Tools & Techniques

1. Burp Suite

Repeater: Test parameter tampering (e.g., price, role).
Turbo Intruder: Exploit race conditions with parallel requests.

2. Manual Testing

Ask: “What if I skip this step?” or “What if I input -1?”

3. Threat Modeling

Diagram workflows and brainstorm abuse cases before coding.

—

Defending Your App

1. Server-Side Validation

Never trust client-side checks:

  # BAD: Client-side check  
  if discount <= 99: apply_coupon()  
  
  # GOOD: Server-side enforcement  
  MAX_DISCOUNT = 99  
  if discount > MAX_DISCOUNT: raise ValidationError("Nice try.")

2. Stateful Workflows

Track steps server-side:

  session['checkout_step'] = 2  # Block skipping to step 3!

3. Rate Limiting

Block coupon spam, password resets, or balance transfers:

  limit_req_zone $binary_remote_addr zone=coupon:10m rate=5r/m;

4. Log & Alert

Monitor anomalies:
- Negative quantities.
- 100 failed logins in 1 minute.

—

Why Developers Miss These Flaws

Focus on code, not design: “It works” ≠ “It’s secure.”
Assumption of honesty: “Users won’t abuse this feature… right?”

—

Final Thoughts

Business logic flaws are the ultimate test of thinking like a hacker. They don’t require exploits—just creativity and a willingness to break the rules. To defend your app:

Question every workflow: “How can this be abused?”
Test manually: Scanners can’t catch design flaws.
Embrace paranoia: Assume users will find loopholes.

Up Next: Day 16: Security Misconfiguration – Defaults, Debug Modes, and Open Doors

—

Rocky out! ✌️

—

P.S. If you’re enjoying this series, share it with your team! Let’s turn “It works” into “It’s secure.”

Discussion Question: What’s the craziest logic flaw you’ve seen? I once upgraded to “admin” by setting plan_id to -1. 😅 Spill your stories below! 👇