AllAboutBugBounty/Misc/Business Logic Errors.md

Business Logic Errors

Introduction

Business Logic Errors are ways of using the legitimate processing flow of an application in a way that results in a negative consequence to the organization.

Where to find

This vulnerability can appear in all features of the application.

How to exploit

1. Review Functionality

   • Some applications have an option where verified reviews are marked with some tick or it's mentioned. Try to see if you can post a review as a Verified Reviewer without purchasing that product.
   • Some app provides you with an option to provide a rating on a scale of 1 to 5, try to go beyond/below the scale-like provide 0 or 6 or -ve.
   • Try to see if the same user can post multiple ratings for a product. This is an interesting endpoint to check for Race Conditions.
   • Try to see if the file upload field is allowing any exts, it's often observed that the devs miss out on implementing protections on such endpoints.
   • Try to post reviews like some other users.
   • Try performing CSRF on this functionality, often is not protected by tokens

2. Coupon Code Functionality

   • Apply the same code more than once to see if the coupon code is reusable.
   • If the coupon code is uniquely usable, try testing for Race Condition on this function by using the same code for two accounts at a parallel time.
   • Try Mass Assignment or HTTP Parameter Pollution to see if you can add multiple coupon codes while the application only accepts one code from the Client Side.
   • Try performing attacks that are caused by missing input sanitization such as XSS, SQLi, etc. on this field
   • Try adding discount codes on the products which are not covered under discounted items by tampering with the request on the server-side.

3. Delivery Charges Abuse

   • Try tampering with the delivery charge rates to -ve values to see if the final amount can be reduced.
   • Try checking for the free delivery by tampering with the params.

4. Currency Arbitrage

   • Pay in 1 currency say USD and try to get a refund in EUR. Due to the diff in conversion rates, it might be possible to gain more amount.

5. Premium Feature Abuse

   • Try forcefully browsing the areas or some particular endpoints which come under premium accounts.
   • Pay for a premium feature and cancel your subscription. If you get a refund but the feature is still usable, it's a monetary impact issue.
   • Some applications use true-false request/response values to validate if a user is having access to premium features or not.
   • Try using Burp's Match & Replace to see if you can replace these values whenever you browse the app & access the premium features.
   • Always check cookies or local storage to see if any variable is checking if the user should have access to premium features or not.

6. Refund Feature Abuse

   • Purchase a product (usually some subscription) and ask for a refund to see if the feature is still accessible.
   • Try for currency arbitrage explained yesterday.
   • Try making multiple requests for subscription cancellation (race conditions) to see if you can get multiple refunds.

7. Cart/Wishlist Abuse

   • Add a product in negative quantity with other products in positive quantity to balance the amount.
   • Add a product in more than the available quantity.
   • Try to see when you add a product to your wishlist and move it to a cart if it is possible to move it to some other user's cart or delete it from there.

8. Thread Comment Functionality

   • Unlimited Comments on a thread
   • Suppose a user can comment only once, try race conditions here to see if multiple comments are possible.
   • Suppose there is an option: comment by the verified user (or some privileged user) try to tamper with various parameters in order to see if you can do this activity.
   • Try posting comments impersonating some other users.

9. Parameter Tampering

   • Tamper Payment or Critical Fields to manipulate their values
   • Add multiple fields or unexpected fields by abusing HTTP Parameter Pollution & Mass Assignment
   • Response Manipulation to bypass certain restrictions such as 2FA Bypass

References

• @harshbothra_