zero-day
termsecurityhacking
A vulnerability unknown to the vendor, with zero days available to have patched it.
A zero-day is dangerous precisely because no fix exists yet: defenders have had zero days of warning. The term stretches to the exploit that uses such a flaw. Once the vendor learns of it and ships a patch, the clock starts and it is no longer a zero-day.
Also known as: 0-day, 0day, zero day, zero-day exploit