CSS Style Tag Injection is a type of vulnerability that allows an attacker to inject malicious code into a website using the CSS style tag. This can lead to various security issues, including cross-site scripting (XSS) attacks and remote code execution. The exploit takes advantage of the fact that the CSS style tag can contain executable code, which is executed by the browser when rendering the web page. This vulnerability can be used to bypass input validation and execute arbitrary code on the target system.