n-form density weight of the levi civita tensor

Question

Why does the n form of levi civita $\epsilon:$=$w_{1}\wedge w_{2} ...\wedge w_{n}$ have a density of weight -1 where $w_{i}$'s are cobasis of some vector basis? I thought this geometrical quantity will have undefined weight which depends upon the vector basis's orientation. So it may have either +1 or -1 as the density weight which depends upon the orientation of the vector basis.