Pre-heat oven to 350˚F and line a 8X8 baking pan with parchment paper and set aside.
In a large bowl add flour, allspice, baking soda, and salt. Whisk to combine and set aside.
In a medium bowl whisk together pumpkin puree, brown sugar, melted butter, vanilla and the egg.
Add the pumpkin mixture to the flour mixture and mix to combine.
Pour the pumpkin batter into the prepared pan and bake for 25 minutes or until the center of the bars comes out clean. Remove from baking pan and allow to cool.
For the frosting:
In a medium mixing bowl add whipped cream cheese frosting and powdered sugar. Using an electric mixer or by hand, mix to combine. The frosting should be slightly stiff.
Frost pumpkin bars, sprinkle with cinnamon and cut into squares before serving.