Zero-day flaw

Also known as zero-day exploit or 0-day, a zero-day flaw is any type of flaw in an operating system, software program, or hardware device that are unknown to the public and often the company affiliated with the product. These flaws become known to the public when a malware program exploits the flaw and compromises the product, the computer, and/or the network connected to the computer. Because the public and sometimes the company is not prepared with fixes or patches to the flaw the exploits can cause serious issues that will remain vulnerable until the company releases a solution to the issue.

Also see: Security definitions, ZERT