if (url.includes('&id=')) ...
And you are just a sysadmin who wants to stop your client for complaining his stupid plugin does not work… So, what you can do about it? If you are using HAProxy 2.0, there is a lot you can do!!
You can use the 'http-request set-query' directive:
http-request set-query %[query,regsub(id=,youare=stupid&id=,g)]