A Zero-Day Exploit refers to a security vulnerability in software that is unknown to the vendor or developer. This means that there are "zero days" for the company to fix the issue before it can be exploited by attackers. These vulnerabilities can allow hackers to gain unauthorized access, steal data, or cause damage to systems. Once a zero-day exploit is discovered, it can be sold on the black market or used in cyberattacks. Companies like Microsoft and Adobe often release patches to address these vulnerabilities once they are identified. However, until a fix is available, systems remain at risk.