Samsung has been testing out versions of Android 8.0 on the Galaxy S8 and Galaxy S8 Plus for months as it inches towards a final release. Last week, the company announced that it would end the beta tests on January 15, but you can get the official version a week early by installing the leaked version right now.
Source: LifeHacker – How to Get the Galaxy S8 Android 8.0 Oreo Update Ahead of Time