need to ignore query string sent by 3rd-party script

Hi, I’ve searched the codex and forums with no luck, so hopefully someone can advise.

I’m building a site with WP as the CMS for a friend and we’re including a form that allows a visitor to join an announcement email list. The join-list script is a CGI provided by the web host — at their own prespecified URL; I can’t alter it. It lets you specify custom URLs for confirmation and error pages (you’ve sucessfully subscribed/unsubscribed; invalid email, etc.), and I’ve created pages for these cases. I have WordPress’ permalink rewrites turned on so pages appear as example.com/postslug/.

The script returns the user to the appropriate custom URLs but also appends a query string in case you want to use the data the user just submitted to do any custom scripting. The problem is that the script collects the user’ name as “name” — so the script sends the user back to a URL like this:

xample.com/list-subscribed/?email=this%40email%2Ecom&name=thisusername&code=success

I believe WordPress uses “name” for the post slug, so this is throwing a 404.

I’ve already asked the host to give me the option to NOT receive that query string; I don’t need it. Haven’t heard back yet. If they fail to respond or can’t accommodate, is there anything I can do about this — some way to ignore the query string beyond the permalink on this handful of pages?) I’d like to I’d like to be able to hand this site off to its owner and let them use their host’s one-click upgrades when new versions of WP come out, so ideally I’d like to avoid modifying WP core files.

Hopefully the host will come through on this, but I figured there might be bright ideas on the forums too. Got any? Thanks!

One more thing — I’ve verified that I can get this to work if I simply don’t request the name, but the site owner would really like to have that too, so I’m giving it a shot ??