SecFox is collection of addons which is can be used to customize any firefox to a security assessment tool. Check http://a4apphack.com/sf1 for few tips and documentation
Automate Firefox. Record and replay repetitious work. If you love the Firefox web browser, but are tired of repetitive tasks like visiting the same sites every days, filling out forms, and remembering passwords, then iMacros for Firefox is the soluti...
The Web Developer extension adds various web developer tools to the browser.
FoxyProxy is an advanced proxy management tool that completely replaces Firefox's limited proxying capabilities. For a simpler tool and less advanced configuration options, please use FoxyProxy Basic.
The User Agent Switcher extension adds a menu and a toolbar button to switch the user agent of a browser.
Use tamperdata to view and modify HTTP/HTTPS headers and post parameters...
View HTTP headers of a page and while browsing.
Cookies manager to view, edit and create new cookies. It also shows extra information about cookies, allows edit multiple cookies at once and backup/restore them.
Simple security audit / Penetration test tool.
Debug Flash/SWF files on the web. Edit properties and inspect elements on the fly. View log output inside the extension. Run AS3 code against the active SWF. Access assets with the Explorer. View AMF calls and Shared Objects and much much more...
Control what gets sent as the HTTP Referer on a per-site basis.
Autofill Forms enables you to fill out web forms with one click.