Zero day attack.

A zero-day (or zero-hour or day zero) attack or threat is an attack that exploits a previously unknown vulnerability in a computer application, one that developers have not had time to address and patch.^[1] It is called a "zero-day" because the programmer has had zero days to fix the flaw (in other words, a patch is not available). Once a patch is available, it is no longer a "zero-day exploit". ^[2] It is common for individuals or companies who discover zero-day attacks to sell them to government agencies for use in cyberwarfare