https://arstechnica.com/information-technology/2021/12/the-log4shell-zeroday-4-days-on-what-is-it-and-how-bad-is-it-really/

Log4Shell is the name given to a critical zeroday vulnerability that surfaced on Thursday when it was exploited in the wild in remote-code compromises against Minecraft servers. The source of the vulnerability was Log4J, a logging utility used by thousands if not millions of apps, including those used inside just about every enterprise on the planet. The Minecraft servers were the proverbial canary in the coal mine.