Knowledgebase
How to fix the update error "Invalid extension update" in Joomla
When you try to upgrade your Joomla 1.6/1.7 with the built-in automatic updater, you may get the error message: Invalid extension update. This error is often displayed to those who have migrated Joomla 1.5 to 1.6/1.7 with jUpgrade. So if you're trying to upgrade Joomla 1.6/1.7 and this current Joomla version is the result of a migration from 1.5 with jUpgrade, you may get the above mentioned message.
A fix that usually helps is to replace a file called update.php. If, for example, your application is installed in a folder called joomla in the root public_html directory on your Joomla hosting account, the path to the file would be public_html/joomla/administrator/components/com_installer/models/update.php. What you need to do is to replace this file with the same file from an installation package for the same version. You can find and download full installation packages and update packages from the download section of the official Joomla site.
Let's say, for example, that you want to update your Joomla 1.7.3 to 2.5 using the automatic updater and you get the error message. Then you should download the 1.7.3 full installation package from download section of the official site. After that you should unzip the archive, find the update.php file in the package (administrator/components/com_installer/models/update.php), and upload the file to the appropriate location on your account overwriting the old file. You can upload the file using an FTP client or through the Files section of the Pixie control panel.
Keep in mind that, for example, not all update packages have this file. The update packages for the different 1.7 versions, for instance, don't have it. Only the full packages that still can be downloaded from the official site (1.7.3 and 1.7.4) have this file. So if you have version 1.7.0, for example, you should use the update.php file from one of the available full packages (e.g. 1.7.3 or 1.7.4).