Html object tag doesn't work on windows 8 with QWebPluginFactory

[ecabot]

I am using the <object> tag using Qt to activate some plugin and it works fine except on windows8.

HTML:
@
<object id="ash3dviewer" type="application/x-ash-viewer3d" data="..." width="800px" height="800px">
Your browser does not support plugins
</object>
@

C++:
@
class PluginsFactory : public QWebPluginFactory {
PluginsFactory(QObject* parent);

virtual QObject* create(
    const QString& mimeType, 
    const QUrl& url, 
    const QStringList& argumentNames, 
    const QStringList& argumentValues) const override;


virtual QList<Plugin> plugins() const override;

};

QWebSettings::globalSettings()->setAttribute(QWebSettings::PluginsEnabled, true);
@

On windows 7 all three methods are called (constructor, plugins, and create) but on windows 8 the create method is never called so my plugin doesn't have a chance to handle the mime type "application/x-ash-viewer3d" properly!

So the <object> tag fails to work and I get "Your browser does not support plugins" on windows8.

It's as if the QWebSettings::PluginsEnabled was disabled "hard" on windows8...

Any hint ?

Note: this is with Qt 4.8.5 (I cannot update to a more recent version unfortunately...)