The first time I heard it, it meant that it was a vuln present since the launch of that version unknown to the publisher, so meaning on day 0 it was possible to exploit it.
Then, when I was studying for a certification I learned they changed the definition to mean it was the number of days a vendor had to patch that vulnerability, and in some cases after being patched these vulnerabilities would get a name assigned to them.
And now, is more of a clickbait word for articles.
How is it a zero day if a patch has been out since November?
It was a 0day back then, I guess, so it (in some unknown magic way) keeps that designation forever, apparently.
Real reason: people want clicks on their slop, so they bait your clicks with nonsense.
Meaningless term nowdays.
The first time I heard it, it meant that it was a vuln present since the launch of that version unknown to the publisher, so meaning on day 0 it was possible to exploit it.
Then, when I was studying for a certification I learned they changed the definition to mean it was the number of days a vendor had to patch that vulnerability, and in some cases after being patched these vulnerabilities would get a name assigned to them.
And now, is more of a clickbait word for articles.