Log4j is a popular open-source logging library used in many Java applications. It helps developers track and record events, errors, and other important information during the execution of their software. By providing a flexible way to manage log messages, Log4j allows for better debugging and monitoring of applications. In December 2021, a critical vulnerability was discovered in Log4j, known as Log4Shell. This security flaw allowed attackers to execute arbitrary code on affected systems, leading to widespread concern and prompting organizations to update their software to protect against potential exploits.