The first Magecart threat they observed was on August 8, 2010. The phenomenon did not take off until last year when British Airways, Ticketmaster, OXO, and Newegg were hit. Magecart attacks are collectively known as Magecart and there are multiple groups currently in the business, some more advanced than others. In one automated attack alone, over 960 stores were compromised in one attack alone. New Magecart actors are likely to appear since Magecart has spread so widely that its infrastructure is common occurrence.
Source: https://www.bleepingcomputer.com/news/security/magecart-impacts-hundreds-of-thousands-of-websites-still-growing/