As GP said, lots of people use this amorphous term differently. Antivirus company ESET, for one, explicitly disagrees with your example: '...The name “zero-day

As GP said, lots of people use this amorphous term differently. Antivirus company ESET, for one, explicitly disagrees with your example: '...The name “zero-day” comes from the fact that no patch yet exists to mitigate the vulnerability being exploited.' https://www.welivesecurity.com/2015/02/11/security-terms-explained-zero-day-mean/ https://www.welivesecurity.com/2015/02/11/security-terms-exp...