A lot of people have experienced some version of this: You sign up for the free one-week trial of some subscription service, only later to be surprised when you get a bill for the deluxe, forever plan. Or you log into a website once, and now your inbox is a flood of promotional emails. All because of a little pre-checked box tucked away, unnoticed.

But what if that pesky, pre-checked box cost you thousands of dollars?

On today's show, how some political campaigns used 'dark defaults' to raise millions of dollars from unsuspecting donors.

Related Episodes: Confused when online shopping? It might be a Dark Pattern

For sponsor-free episodes of The Indicator from Planet Money, subscribe to Planet Money+ via Apple Podcasts or at plus.npr.org.

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