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. 'vmlframe' defines a frame for an external shape. Attackers can use 'vmlframe' to implement XSS attack. This rule detects '<vmlframe src=' in HTTP request. This rule supports to defend the A3: Injection of OWASP Top 10 - 2021. Other reference:None