"Although the term "zero-day" initially referred to the time since the vendor had become aware of the vulnerability, zero-day vulnerabilities can also be define

"Although the term "zero-day" initially referred to the time since the vendor had become aware of the vulnerability, zero-day vulnerabilities can also be defined as the subset of vulnerabilities for which no patch or other fix is available." - Source: https://en.wikipedia.org/wiki/Zero-day_vulnerability https://en.wikipedia.org/wiki/Zero-day_vulnerability