With 1-Down, invasive Australian species descended from pack animals introduced in the 1800s and abandoned to run wild in the Outback when motor vehicles made them obsolete
8A
Park place?
Down
1D
See 7-Across
2D
One who may ask if you've tried turning it off and then back on again
3D
It's mostly water and electrolytes
4D
File format whose pronunciation debate brings out the most insufferable pedants and logical fallacy deployers on both sides