Zero-day

Full definition of zero-day

Adjective

1. (computing) Pertaining to the day on which software is released.
• 2003, John Viega, Matt Messier, Secure Programming Cookbook for C and C++If your software is popular and has a high demand, you will want to defend against the "zero-day" cracker.
• 2005, Valdes et al, Recent Advances in Intrusion DetectionAutomatically creating reliable signatures of zero-day exploits is the focus of intense research efforts.