Philips is releasing a new hue bridge firmware upgrade starting on April 20th 2016 for the US. This update will feature a security upgrade and functionality for the new Philips hue application that will be released in Spring 2016.
The security update changes the authentication process for third party hue applications to help make the system more secure. So third party applications like On Switch, Hue Disco, Hue lights, etc will have to upgrade their application to meet the new security requirements. Philips has been working with application developers on this update since September 2015 so most of the major third party applications have already been updated.
Click here for a list of applications that have and have not been updated.