Major Security Bug w/ Usage of Heads

"This video demonstrates a security issue with Custom Player Heads."
As appointed in the video. I personally don't know how long it has been here for.

This needs to be fixed or something wrong may occur later on.

Video demonstration created by CrushedPixel: (Not my video!)
https://www.youtube.com/watch?v=EO6VXy_4y1Y

PLEASE WATCH AND SEE IF IT CAN BE FIXED

Thank you for reading this, good luck fixing it!

P.S - Sorry if this had been stated before by somebody else.