The Known Unknowns” to explain the dynamics behind the market of zero-day exploits. The market is able to provide 85 exploits per day, a concerning number for the security industry. Governments have recently created dedicated cyber units to the discovery and exploitation of unknown vulnerabilities, but in many cases this precious knowledge is sold by private entities on the underground. On any given day over the past three years, privileged groups have had access to at least 58 vulnerabilities targeting Microsoft, Apple, Oracle, or Adobe.
Source: https://thehackernews.com/2013/12/growing-market-of-zero-day.html