"Jack Dorsey just tweeted out "Day 0" today. What the hell is THAT supposed to mean? Zero day?"
https://www.reddit.com/r/conspiracy/comments/p272i3/jack_dorsey_just_tweeted_out_day_0_today_what_the/
"In August 2016, a group calling itself Shadow Brokers released a cache of top secret cyber spying capabilities almost certainly belonging to the U.S. National Security Agency (NSA). Out of the fifteen exploits in the cache, several appear to be previously unknown vulnerabilities (a so-called zero day or 0day vulnerability)."
https://jia.sipa.columbia.edu/online-articles/healey_vulnerability_equities_process
"When the NSA discovers a new method of hacking into a piece of software or hardware, it faces a dilemma. Report the security flaw it exploits to the product's manufacturer so it gets fixed, or keep that vulnerability secret---what's known in the security industry as a "zero day"---and use it to hack its targets, gathering valuable intelligence"
https://www.wired.com/2016/08/shadow-brokers-mess-happens-nsa-hoards-zero-days/
"Chinese state hackers cloned and started using an NSA zero-day exploit almost three years before the Shadow Brokers hacker group publicly leaked it in April 2017."
https://www.bleepingcomputer.com/news/security/chinese-hackers-used-nsa-exploit-years-before-shadow-brokers-leak/
Shadow Brokers launch subscription service for stolen exploits, zero-day leaks
https://www.zdnet.com/article/shadowbrokers-launch-subscription-service-for-fresh-exploits-zero-day-leaks/