Google Domain Name Exploit

URL redirection: Some members of the security community argue that open redirectors are a security issue. The common argument in favor of this view is that some users, when presented with a carefully crafted link, may be duped into thinking that they will be taken to a trusted page - but will be not be attentive enough to examine the contents of the address bar after the redirection takes place.

On the other hand, we recognize that the address bar is the only reliable security indicator in modern browsers; and consequently, we think that any user who could be misled by a URL redirector can also be tricked in other ways, without relying on any particular trusted website to act as a relying party.

The reward panel will likely deem URL redirection reports as non-qualifying: while we prefer to keep their numbers in check, we hold that the usability and security benefits of a small number of well-implemented and carefully monitored URL redirectors tend to outweigh the true risks

> "Keep a hash map of URLs. In other words, instead of having the URL in the query string, have a key that refers to that URL there. In this way, only the URLs for the keys that YOU define are redirectable."

Huh? I wish you would expand on this a little bit.