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# Excessive Trust in Client-Side Controls
Excessive Trust in Client-Side Controls notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### Excessive Trust in Client-side Controls
**Description of lab**
This application does not properly validate the data sent by the client. / It is possible to exploit a logical flaw in the purchasing process in order to change the price of a product. / The objective is to buy a \*\*
Identifier provided:
* **User**: wiener
* **Password**: peter
**Behavioral analysis**
A shopping cart is available on the website
When adding a product to the basket, a **POST** query is sent with several parameters, including price.
Example of a query observed during a standard addition to the basket:
```bash
productId=1&redir=PRODUCT&quantity=1&price=133700
```
The **price** parameter is fully controlled by the client and is not properly checked on the server side.
**Exploitation**
By manually changing the value of the **price** parameter in the query, for example:
```bash
productId=1&redir=PRODUCT&quantity=1&price=0
```
the server accepts the request without performing strict validation.
**Result**
The product is added to the basket and the purchase can be validated, despite a handled price on the customer side. / This demonstrates an excessive reliance on browser-side controls, allowing the expected business logic to be circumvented.
---
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