A zero-day vulnerability is a vulnerability in a software system or device that has been disclosed but is not yet patched. It is worth mentioning that sometimes a zero-day vulnerability will remain undisclosed to be exploited by cybercriminals and intelligence agencies. An exploit that attacks a zero-day vulnerability is called a zero-day exploit. Because they were discovered before security researchers and software developers became aware of them—and before they can issue a patch—zero-day vulnerabilities pose a higher risk to users for the following reasons: Cybercriminals race to exploit these vulnerabilities to cash in on their schemes Vulnerable systems are exposed until a patch is issued by the vendor. Zero-day vulnerabilities are typically involved in targeted attacks; however, many campaigns still use old vulnerabilities. In the hacking world, these invisible backdoors have different sci-fi names: they call them zero-days (or 0 days), pronounced “oh-days.” For the unindoctr