Intercept HTTP traffic from Firefox extensions
Up till now it hasn't been possible for Firefox extensions to intercept HTTP traffic.
But with the landing of a fix in bug 430155 - new nsHttpChannel interface to allow examination of HTTP data before it is passed to the channel's creator. it's now possible.
The fix is gonna be in Firefox 3.1 and perhaps also in Firefox 3.0.3.
A new version of Firebug that uses this new feature is also in the making.