Do not worry as they are not illegitimate. It is actually a token of apology from EA as the game developer looks to fix a major bug in FIFA 14. The bug is the one that prevents the players from searching in the transfer market. The only way around it is if the player has an eye for talent, like Arsene Wenger.
At the moment, the fix is nearing its completion. EA revealed that it is in the final stages of development and the issue might just be fixed by the end of next week.
Every Ultimate Team created before April 1 will get to enjoy the Gold Rare pack and players have up to April 11 to redeem their pack. Following that day, the golden treat will disappear entirely if unclaimed.