Lesson Plan Title: How to Exploit Hidden Fields

Concept / Topic To Teach:

Developers will use hidden fields for tracking, login, pricing, etc.. information on a loaded page. While this is a convenient and easy mechanism for the developer, they often don't validate the information that is received from the hidden field. This lesson will teach the attacker to find and modify hidden fields to obtain a product for a price other than the price specified

General Goal(s):

The user should be able to exploit a hidden field to obtain a product at an incorrect price.

Figure 1 Lesson 4

Solution:

To change the hidden field you need to start your favorite HTTP Interceptor. You can use WebScarab from OWASP to intercept the request and change the hidden field. Configure your browser to use a local proxy. In Internet Explorer you can do this via “Tools” – “Internet Options” – “Connections” – “LAN Settings”. You must define proxy “localhost” with port 8008.

Figure 2 Set local proxy in Internet Explorer

Start WebScarab

Figure 3 Intercept request with WebScarab

Figure 4 Change the Price variable to 1

Figure 5 Lesson 4 Completed

Solution by Erwin Geirnaert |