Version 2.3.9.1 is available upstream. Please consider updating! It seems that version 2.3.9.1 is available upstream, while the latest version in the Gentoo tree is 2.3.8. You think this warning is false? Read more about it here.
This package uses attoparsec for parsing the actual contents of the HTTP connection. It also provides higher-level functions which allow you to avoid direct usage of conduits. See <http://www.yesodweb.com/book/http-conduit> for more information.