Zeroday Emergency Response Team
In computer security, the Zeroday Emergency Response Team (ZERT) was a group of volunteer security researchers who produced emergency patches for zero day attack vulnerabilities in proprietary software. They came to public notice in late September 2006 with a patch for that month's Vector Markup Language vulnerability before Microsoft, later producing a patch for older versions of Microsoft Windows which are no longer supported by Microsoft.
Source: Wikipedia — Zeroday Emergency Response Team (CC BY-SA 4.0)