The rule "ReverseShell Upgrade From WebShell" is designed to detect instances where attackers attempt to upgrade from a web shell to a reverse shell on a system. It specifically analyzes web application firewall logs for unusual command execution patterns, particularly those related to PowerShell, MSHTA, and various Windows executables that are often used in exploitation attempts. The detection logic uses a combination of search terms and regular expressions to identify network activity indicative of this type of shell upgrade, focusing on script terms that commonly appear in malicious contexts, such as parameters indicating non-interactive shell execution, encoded commands, and file downloads typical of exploit kits. By filtering the web data logs, it enables security teams to pinpoint the source, nature, and potential impact of these threats, enhancing incident response capabilities and mitigative measures against such upgrades.