A zero-day exploit is a type of computer attack that exploits
a software vulnerability before that vulnerability is known to the public
or the softwareʼs developer.
Zero-day exploits are very valuable to hackers and cybercriminals
because they are unknown — all systems running the affected software
are vulnerable, so the attack is likely to succeed.
The term “zero-day”
refers to the idea that the developer has had zero days between learning
of the vulnerability and the attack occurring.