Zero-day - Code Curmudgeon

A zero-day is a hack that has been newly published. The zero refers to the fact that it’s published before a fix or patch is ready and available. Once there is a known patch then it just becomes a known vulnerability. Further though, if you don’t keep your patches up-to-date then all vulnerabilities are zero-day problems for you.

Definitioner

Zero-day

A zero-day is a hack that has been newly published. The zero refers to the fact that it's published before a fix or patch is ready and available. Once there is a known patch then it just becomes a known vulnerability. Further though, if you don't keep your patches up-to-date then all vulnerabilities are zero-day problems for you.

vulnerability

This is a tricky word, especially in application security or cybersecurity. The simple definition in a software context is that the code has some problem that could be exploited by someone at some point. Some think of it as a piece of code with a proven exploit, IE a static analysis violation with a stack trace and values used. This is a very narrow definition that probably doesn't help improve the state of the art. I prefer the idea that it's code that is exploitable based on the body of knowledge (as encapsulated in software coding standards).