Everything you need should be in here somewhere 🙂
var myLayer = app.project.item(1).layer(1);
var myMask = myLayer.property(“ADBE Mask Parade”).property(1);
var myProperty = myMask.property(“ADBE Mask Shape”);
var myShape = myProperty.value;
myShape.vertices = [[5,5],[5,45],[45,45],[45,5]];
myShape.inTangents = [[0,0],[0,0],[0,0],[0,0]];
myShape.outTangents = [[0,0],[0,0],[0,0],[0,0]];
myShape.closed = true;
myProperty.setValue(myShape);
Dan