Heat the oven to 350°F. Line a quarter sheet pan or an 8-inch square metal pan with parchment paper.
Mix the cake mix, eggs, melted butter, and vanilla in a large bowl until a thick dough forms.
Gently fold 1 cup of the whole pumpkin candies into the dough. Spread the dough evenly in the prepared pan. Press the remaining 1/2 cup of candies over the top.
Bake for 20 to 25 minutes, until the edges turn golden and the center looks set. Check early so the candy does not overbrown.
Cool completely in the pan, then lift out and cut into 12 bars.