Why am I receiving a pop-up while playing games on PCH.com/games that asks me to enter a passphrase?

Why am I receiving a pop-up while playing games on PCH.com/games that asks me to enter a passphrase?

Every 10 games that you play, you will be prompted with this pop up.  Don't be alarmed, though! It is just an extra security procedure used to make sure that all of our fans can enjoy our games in a fair and equal way.  Simply enter the passphrase whenever you are prompted with the pop up to continue playing.