A zero-day refers to a software vulnerability or security flaw that is unknown to the software vendor or has no available patch or fix. It is called "zero-day" because developers have zero days to fix the vulnerability before it is exploited. Zero-day vulnerabilities are highly valuable to attackers as they can be leveraged to launch targeted attacks before security measures are in place.
A zero-day refers to a software vulnerability or security flaw that is unknown to the software vendor or has no available patch or fix. It is called "zero-day" because developers have zero days to fix the vulnerability before it is exploited. Zero-day vulnerabilities are highly valuable to attackers as they can be leveraged to launch targeted attacks before security measures are in place.