This forced a massive shift in how we approach supply chain security. It proved that securing the core application was not enough; third-party extensions, API endpoints, and even the administrative users themselves were all viable vectors of catastrophic failure. The Legacy of Magento 1.x
You're looking for information on a Magento exploit.
The exploits targeting Magento 1.9.0.x served as the official birth certificate for Magecart—a syndicate of hacker groups specializing in digital credit card skimming. Instead of breaking into a network to steal a static database of old credit cards, attackers realized they could simply inject a few lines of JavaScript into the checkout page. As customers typed their 16-digit numbers in real-time, the script silently copied the data and sent it to an attacker-controlled server.
(which suffered from a famous remote code execution vulnerability) or refers to the classic Magento 1.9.0.x era vulnerabilities.