If the image upload no longer works in some areas of the Magento backend and the error "ReferenceError: Uploader is not defined" appears in the error console, this may be due to several required JavaScript files not being included. These files have become mandatory following the switch from Flash to HTML uploaders with Magento CE 1.9.3 and the corresponding patches.
Normally, the files should be included automatically via the "default" layout handle using
/app/design/adminhtml/default/default/layout/main.xml
However, some areas do not use this handle and therefore need to be adjusted separately. This applies, for example, to image uploads via widget instances, in addition to some plugins. What needs to be done? We include 4 JS files in
/app/design/adminhtml/default/default/layout/widget.xml
using the following statements (handle adminhtml_widget_instance_edit, reference "head"):
<action method="addJs"><file>lib/uploader/flow.min.js</file></action>
<action method="addJs"><file>lib/uploader/fusty-flow.js</file></action>
<action method="addJs"><file>lib/uploader/fusty-flow-factory.js</file></action>
<action method="addJs"><file>mage/adminhtml/uploader/instance.js</file></action>
This is enough to get the file uploader working again. Seen in Magento CE 1.8.0.0.
