To put these zero-day definitions together, zero-day vulnerabilities leave us susceptible to zero-day attacks, which are carried out by zero-day exploits. Sometimes written as 0-day, zero-day definitions run the gamut:

What is zero-day? The term “zero-day” refers to a newly discovered software vulnerability and the fact that developers have zero days to fix the problem because it has been - and has the potential to be - exploited by hackers.