During a recent security assessment, a vulnerability was found in a common OS.

A zero-day vulnerability is a security flaw that is unknown to the vendor and the public, and therefore has no patch or fix available. A zero-day attack is an exploit that takes advantage of a zero-day vulnerability before the vendor or the security community becomes aware of it. A zero-day attack can cause serious damage to a system or network, as there is no defense against it until a patch is released. References:

https://resources.infosecinstitute.com/certification/security-domain-1-threats-attacks-and-vulnerabilities/

https://www.linkedin.com/learning/comptia-security-plus-sy0-601-cert-prep-1-threats-attacks-and-vulnerabilities/zero-days-and-the-advanced-persistent-threat

https://www.professormesser.com/security-plus/sy0-501/zero-day-attacks-4/