This codelab is built around Jarlsberg /yärlz'·bərg/, a small, cheesy web application that allows its users to publish snippets of text and store assorted files. "Unfortunately," Jarlsberg has multiple security bugs ranging from cross-site scripting and cross-site request forgery, to information disclosure, denial of service, and remote code execution. The goal of this codelab is to guide you through discovering some of these bugs and learning ways to fix them both in Jarlsberg and in general.

The codelab is organized by types of vulnerabilities. In each section, you'll find a brief description of a vulnerability and a task to find an instance of that vulnerability in Jarlsberg. Your job is to play the role of a malicious hacker and find and exploit the security bugs. In this codelab, you'll use both black-box hacking and white-box hacking.