A vulnerability is a fault in a programs implementation that can be used by attackers to gain unauthorized access to data, inject malicious code or put a system out of operation. In some cases, an exploit is used on a mass scale that is, cybercriminals try to use it to attack a broad range of systems. The more sophisticated and popular the program the higher the chances of vulnerabilities being found in it. An entire sector of the cybercriminal underworld specializes in finding and selling vulnerabilities.”]
Source: https://securelist.com/you-cant-be-invulnerable-but-you-can-be-well-protected/73160/