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We want Googlers to have a firm understanding of the threats our services face, as well as how to help protect against those threats. We work toward these goals in a variety of ways, including security training for new engineers, technical presentations about security, and other types of documentation. We also use codelabs — interactive programming tutorials that walk participants through specific programming tasks.

One codelab in particular teaches developers about common types of web application vulnerabilities. In the spirit of the thinking that “it takes a hacker to catch a hacker,” the codelab also demonstrates how an attacker could exploit such vulnerabilities.

We’re releasing this codelab, entitled “Web Application Exploits and Defenses,” today in coordination with Google Code University and Google Labs to help software developers better recognize, fix, and avoid similar flaws in their own applications. The codelab is built around Jarlsberg, a small yet full-featured microblogging application designed to contain lots of security bugs. The vulnerabilities covered by the lab include cross-site scripting (XSS), cross-site request forgery (XSRF) and cross-site script inclusion (XSSI), as well as client-state manipulation, path traversal and AJAX and configuration vulnerabilities. It also shows how simple bugs can lead to information disclosure, denial-of-service and remote code execution.

The maxim, “given enough eyeballs, all bugs are shallow” is only true if the eyeballs know what to look for. To that end, the security bugs in Jarlsberg are real bugs — just like those in many other applications. The Jarlsberg source code is published under a Creative Commons license and is available for use in whitebox hacking exercises or in computer science classes covering security, software engineering or general software development.

To get started, visit http://jarlsberg.appspot.com. An instructor’s guide for using the codelab is now available on Google Code University.