Most Perl programmers at some point in their career are involved in a project that includes a bit of Web development. One of the Firefox plug-ins that I occasionally find useful for the debugging and testing of Web applications is the Tamper Data plug-in for Firefox. In particular, from a debugging perspective it allows you to capture HTTP and HTTPS headers as well as POST parameters, which can allow you to verify the requests that are being sent to your Web application. On the testing side, some basic security testing can be done as well, since it allows you to modify captured HTTP/HTTPS headers and POST parameters prior to transmission. While someone that is heavily involved in the security testing of Web applications, would likely be better served by more robust intercepting proxies (e.g. Burp Proxy, etc) it is a nice plug-in to use to introduce people to some of the basic techniques that can be used to test Web application security. An example of a captured Facebook login request can be seen below.
Notice, how it shows the different POST parameters and their values? Any one of these parameters in the request could then be modified and submitted to the site. Once the “OK” button is clicked, the request will be forwarded to the Web application, including whatever modifications that you have made.