UPDATE 6/25/2008: I’ve made a few changes to the source code and updated the executable to deal with some compatibility issues with extensions that don’t employ the “em:” prefix in install.rdf. Also, the application should no longer leave the temp directory around if it fails to patch the file. If you’re encountering either of these issue, please try the newer version.
If you follow the beta and RC builds of Firefox, you’ve probably found that at least a few of your add-ons from previous versions are blocked with the new builds, ostensibly for compatibility reasons. If you’ve done a bit more digging, you’ve probably found that there are some ways around this blocking, which involve opening the .xpi extension files (which is really just a renamed .zip), making changes to the maxVersion attribute of install.rdf, and updating the archive.
While this isn’t a terribly difficult process, it can be a bit of pain if you have a number of .xpi’s that you want to update. To make this process a bit easier, I threw together a quick application that makes the process a good deal simpler, by allowing you to drop target one or more xpi files and have them automatically patched up to whatever version you specify.
HigherFox simply extracts the contents of the .xpi files that are dragged onto it, updates the maxVersion attribute for Firefox (it doesn’t touch values for Flock, Netscape, etc.), and then repacks all the components into a new archive that is save at the source location as <original_xpi_name>_patched.xpi.
It goes without saying that patching .xpi files is a poor alternative to installing official releases from the author. Moreover, there is no guarantee that the extension will actually be compatible in the version of Firefox you’re running. However, if you’re still waiting for your favorite plug-in to be officially updated, this might just be the hack that you’re looking for.
Thanks to DotNetZip for their nice little ZIP library that let me keep this in a single executable!