> For the complete documentation index, see [llms.txt](https://ssrd.gitbook.io/securebank/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ssrd.gitbook.io/securebank/miscellaneous/simultaneous-request.md).

# Simultaneous Request

## Challenge

Get a negative account balance by buying a product.

## Solution

‌Quickly buy two items in a very short time from the store. You need to have enough money so that you can buy the first item, but not enough money to buy the second item.

You will find the flag in the response header.