I simulated the behaviour of the search engine by disabling the cookie support in the browser. Originally, the View Issues page went into an infinite loop when visited. The reason is that the page re-directs to view_all_set if the cookie value is invalid. view_all_set then re-directs back to the view issues page. Disabling the re-direct will continue the flow and hence the filter_get_rows() will be called and return a non-filtered result set which is what is required. However, this may cause other problems in the cases where cookies exist but are really invalid.

check to see if the cookie does not exist

if ( !filter_is_cookie_valid() ) {
#print_header_redirect( 'view_all_set.php?type=0' );
}

The main page always worked, the bug view pages gave me access denied once, then worked without a problem.

Reminder sent to Narcissus

Narcissus, what do you recommend for fixing this issue? The idea is to allow search engines to crawl as much of Mantis as possible and hence people will be able to reach the issues directly from the search engines.

As you said, Victor:

I've removed the various redirect-if-cookie-invalid calls, since an invalid cookie is really not a bad thing. Just assume defaults if the cookie is not valid. If a cookie is invalid, it will be set again if the user attempts any change (to the filter for example).

The necessary changes are checked in, and so far it works well.