Hello Randall,
If it's for a single plugin, the easiest way is to use `mvn dependency:tree` to check if you are using Struts or not. Usually if you include Struts indirectly (through transitive dependencies) there is low likelihood that you are effectively using it. Most of the Jenkins plugins are using only Stapler for their HTTP request handling, without any other framework (like Struts).
If you want to know about an instance of Jenkins with its plugins, I would recommend to use a regular security scanner (SCA) to see if they are finding anything there.
Now, if you are not sure, you can still contact the security team, but I will ask you to provide more details, like which plugin, which CVE, and your doubts.
Best regards,
Wadeck Follonier
Jenkins Security officer