The psychic paper in the TV show "Doctor Who" displays whatever the Doctor needs it to show at any given time. The Java vulnerability Neil Madden exposed is a digital version of this. Dr Mike Pound explains. Neil Madden's blog: https://neilmadden.blog/2022/04/19/psychic-signatures-in-java https://www.facebook.com/computerphile https://twitter.com/computer_phile This video was filmed and edited by Sean Riley. Computer Science at the University of Nottingham: https://bit.ly/nottscomputer Computerphile is a sister project to Brady Haran's Numberphile. More at http://www.bradyharan.com