Last modified: 2014-04-20 21:50:33 UTC
The given error message indicates a server problem, however, it is just a misspelled URL.
Raw "&" appearing in URLs is currently blocked with a 403 to prevent some infinite loops from bad spiders we were seeing. We might be able to remove this now, though, as the RSS/Atom feed links involved have changed.
The bug also happens if you search for "&" on a Wikimedia site: http://en.wikipedia.org/wiki/Special:Search?search=%26amp%3B
*** Bug 16053 has been marked as a duplicate of this bug. ***
*** Bug 23945 has been marked as a duplicate of this bug. ***
AFAICS this has been fixed.