Magecart is the same group of digital credit card skimmers which made headlines last year for carrying out attacks against some big businesses including Ticketmaster British Airways, and Newegg. Magecart Group 12 hacked and inserted its skimming code into a third-party JavaScript library, enabling all websites using that script to load the malicious code. The code then sends the skimmed payment data, the random number (E-tag), and the e-commerce website’s domain to a remote server through HTTP POST, with Base64 coding on the entire, sent date.
Source: https://thehackernews.com/2019/01/magecart-hacking-credit-cards.html