DNSUnpinning Firefox extension

The DNSUnpinning Firefox extension was mostly an excuse to learn how to write a Firefox extension. All it does is provide an option in the Tools menu to disable or enable DNS caching/pinning. This is a rather complex topic involving the same-origin policy in Web browsers. Christian Matthies has a pretty good description of DNS pinning.

This extension is probably only useful to Web application developers, Web application security researchers, and perhaps the occasional system/network administrator of a load-balanced Web service. The extension was written based on a template created by Ted Mielczarek's Firefox/Thunderbird Extension Wizard (which I learned about upon reading a recent Linux Journal article).

The extension merely creates the network.dnsCacheEntries preferences option and sets it to zero at browser startup. The Tools menu item sets and clears this preference option (a description of this option can be found in a TweakGuide post).

To install the DNSUpinning extension, download it (below) and save it to a file on your computer. Then do File->Open from the Firefox menu and browse to the downloaded file.

DNSUnpinning v1.0