Sites belonging to a reseller of tickets for Euro Cup and the Tokyo Summer Olympics have been infected with JavaScript that steals payment card details. The malicious code that steals card data from online stores at checkout is commonly known as MageCart since it initially targeted sites running the Magento e-commerce platform. On one of the websites, the malicious code survived for at least 50 days, while on the other it lasted for two weeks. MageCart was hiding in a legitimate library called Slippry (a responsive content slider for jQuery) and activated when the slider loaded.
Source: https://www.bleepingcomputer.com/news/security/euro-cup-and-olympics-ticket-reseller-hit-by-magecart/