The 6Sec app is the latest workaround created for the Windows Phone Store to replace a popular app that so far has not been developed for the Windows Phone platform. With no official Instagram app for the platform, quite a few third party apps have sprung up. Instance is considered to be among the best of the lot, and is working on a way to allow Windows Phone 8 users to upload videos to Instagram. Right now, WPGram allows users to view Instagram videos along with still pictures, but will not allow you to upload videos to the Instagram site.
source: 6Sec via WMPoweruser