Google Code-in

[Note, this is a little more involved than some of the other GCI tasks]

The file includes/Feed.php in MediaWiki core is using php as a templating language. For example, in RSSFeed::outHeader() it is directly outputting XML mixed with things like <?php print $this->getTitle(); ?>

It also seems to have inconsistent escaping (For example, calling wfExpandUrl() on a value already passed through htmlspecialchars(), where htmlspecialchars() is always supposed to be the last thing you do.

It would be nicer if this used Mustache) and was consistently escaped using Mustache's double brace syntax. See the folder includes/templates for example Mustache templates, and $templateParser->processTemplate() for examples of where Mustache is used in MediaWiki. And https://mustache.github.io/mustache.5.html

You are expected to provide a patch in Wikimedia Gerrit. See https://www.mediawiki.org/wiki/Gerrit/Tutorial for how to set up Git and Gerrit.