The woman—who has only been identified by her surname, Wang—was having a meal with friends at a hotpot restaurant in Kunming, a city in southwest China. When everyone’s selections arrived at the table, she posted a photo of the spread on the Chinese social media platform WeChat. What she didn’t notice was that she’d included the QR code on her table, which the restaurant’s customers use to place their orders.

Even though the photo was only shared with her WeChat friends list and not the entire social network, someone—or a lot of someones—used that QR code to add a ridiculous amount of food to her order. Wang was absolutely shocked to learn that “her” meal soon included 1,850 orders of duck blood, 2,580 orders of squid, and an absolutely bonkers 9,990 orders of shrimp paste...