Patch releases of both the Web Developer and User Agent Switcher extensions have been released for Firefox. These releases primarily add support for Firefox 4 to both extensions as well as fixing a few issues in Web Developer including ‘View Style Information’ being vulnerable to a cross site scripting attack. The full list of changes to the Web Developer extension can be found in the release notes.
I had originally hoped to release version 1.2 of the Web Developer extension in time for Firefox 4. Version 1.2 will merge the Firefox and Chrome codebases of the extension, as well as adding new features and fixing a number of issues. However, this is still in development which is why I have released this minor update to make sure that Web Developer is at least compatible with Firefox 4.