Stealing other people's Masteries [GAMEPLAY]

This is potentially gamebreaking

How to recreate:

1. Make a teambuilder lobby
2. Choose a champion, but do NOT choose a role or position
3. Go to your friends list and view someones masteries
4. Click the icon in the top left
5. Click return to lobby button
6. Choose role and position
7. Choose masteries(you will now have all the masteries of the chosen friend)