The XZ Exploit was an incredible near miss. Dr Richard G Clegg of Queen Mary University London explains how a seemingly helpful contributor hid some code in part of a ubiquitous piece of software. Computerphile is supported by Jane Street. Learn more about them (and exciting career opportunities) at: https://jane-st.co/computerphile This video was filmed and edited by Sean Riley. Computerphile is a sister project to Brady Haran's Numberphile. More at https://www.bradyharanblog.com