ZERO-DAY (FAULT)
A zero-day flaw is an application vulnerability that is known only to attackers who exploit it for their own benefit. Since it is still unknown to the publisher of the targeted application, the vulnerability cannot be corrected, and potential victims who are not informed of its existence cannot take compensatory measures. This allows attackers to compromise many systems easily and without being detected. The rarity of such zero-day flaws, especially when they concern updated versions of major operating or mobile systems, makes them particularly sought after. There is a whole market — official and unofficial — that offers such flaws and their price can rise to several hundred thousand euros, or even for some of them to more than a million euros.
With such a reputation and being so highly valued, zero-day flaws have become the stars of the dunces.