Description: Weiß-grün mit Wappen der Steiermark. Dienstflagge der Steiermark. White-green with coat of arms of Styria. Flag of the state of Styria.

Source: Image:Steiermark Wappen.svg by David Liuzzo, with colour modifications since this is a flag (i.e. no gradients etc).
No machine-readable source provided. Own work assumed (based on copyright claims).
No machine-readable author provided. Yaddah assumed (based on copyright claims).