Called "emergency" cupcakes because they're for emergencies, as in "Mom, I forgot to tell you that you're supposed to bring cupcakes to school today...
Preheat the oven to 375°F. Line 12 regular-sized muffin tin with paper or foil liners.
In a blender jar, combine the flour, cocoa, sugar, baking soda, and salt. Cover with the lid and blend on medium-speed until blended. Pour in the water, oil, egg and vanilla. Cover with the lid and blend on medium-high speed until smooth and well blended, stopping to scrape down the sides once or twice.
Pour the batter into the prepared muffin tin, dividing evenly. Bake until a toothpick inserted into the center of one cupcake comes out clean, about 15 to 17 minutes.
Transfer the pan to a rack to cool for about 10 minutes, and then carefully remove the cupcakes from the pan and set them on the rack to cool completely before frosting.