Cross-site scripting(XSS) is a type of computer security vulnerability tipically found in Web application. XSS enables attackers to inject client-side scripts into Web pages viewed by other users. HTML tag '<embed>' is used to define the content inserted in webpage, such as plugins. Attackers can use '<embed>' to implement XSS attack. This rule detects '<embed' in HTTP request. This rule supports to defend the A3: Injection of OWASP Top 10 - 2021. Other reference:None