In order to comply with the requirements of app sandboxing, some Aperture plug-ins may need to be updated by the developer. If you encounter a plug-in that no longer operates properly when you use it with Aperture 3.4, contact the developer of the plug-in directly and ask when a version compatible with app sandboxing will be available.
Aperture 3.4 and later: Some third-party plug-ins are no longer compatible
The App Sandbox is one of the security features of OS X Lion v10.7.5 and OS X Mountain Lion v10.8. It isolates apps from critical system components of your Mac, your data, and other apps in order to keep your Mac more secure from malicious software. Plug-ins that do not comply with the requirements of app sandboxing may not operate properly with Aperture 3.4 and later. When attempting to use an affected plug-in, you may be presented with an alert dialog. In some cases, you may be able to dismiss the alert message and use the plug-in anyway. In other cases, the plug-in may have no effect, or may cause Aperture to quit unexpectedly.