Preheat the oven to 350 degrees F (175 degrees C). Line two baking sheets with parchment paper.
Combine cake mix, pudding mix, flour, vegetable oil, eggs, and cornstarch in a large bowl; beat with an electric mixer until well blended. Fold in chocolate chips, cherries, marshmallows, sprinkles, and pecans; do not overmix. Use a cookie scoop to drop spoonfuls of dough 2 inches apart onto the prepared baking sheets.
Bake in the preheated oven until bottoms are just golden, 8 to 10 minutes. Cool on the baking sheets for 1 minute, then remove to a cooling rack to cool completely, about 25 minutes.