For an integer $m > 1$, let us define the action
$$
f: X_i \to (1+X_i)^{m} - 1
$$
on $C[[X_1,...,X_N]]$, where $C$ is the complex number field. Consider the analytic manifold $V(I)$ defined by the ideal $I$ in $C[[X_1,...,X_N]]$.
Question: For which $V(I)$ is it possible that $V(I)$ is stable under the action $f$? Equivalently for which $I$ do we have that $f(I) = I$?