File path traversal, traversal sequences blocked with absolute path bypass

Description

This lab contains a file path traversal vulnerability in the display of product images. The application blocks traversal sequences but treats the supplied filename as being relative to a default working directory.

Reproduction and proof of concept

Use Burp Suite to intercept and modify a request that fetches a product image.
Send to Repeater and modify the filename parameter, giving it the value /etc/passwd.
The response contains the contents of the /etc/passwd file:

Traversal

Exploitability

An attacker will need to retrieve the contents of the /etc/passwd file.