The Log4j vulnerability, known as Log4Shell, is a critical remote code execution (RCE) vulnerability that affects all versions of Log4j2 from 2.0-beta9 to 2.14.1. The vulnerability was discovered in Minecraft and has been spotted in various applications, including Apache Struts 2, Apache Solr, and Spring Boot applications. It allows attackers to inject malicious code into the logging framework, which can lead to RCE attacks. To remediate the vulnerability, users should update to Log4j version 2.17.1 or later, or set the system property log4j2.formatMsgNoLookups to true. Scanning applications with tools like Snyk Open Source can help identify vulnerable versions of Log4j and provide remediation advice.