David, I haven't seen any issues with LinkClick.aspx being abused by hackers as they aren't really "open" redirects, it is doing a redirect with information found in the database based on the querystring parameters, not redirecting directly to the parameters passed to the page.

I've seen attempts at this type of redirection on the Engage: Publish module, which used to use some redirection, but even then it was using an ID, and not a URL being passed in for the redirection.

I don't know if the UDT is doing something different than linkclick, but I imagine it's using the core DNN functionality.