Do I need to update PHP ASAP? Sorry, I only have a German article: http://m.heise.de/security/meldung/Wichtige-Sicherheitsupdates-fuer-PHP-2557586.html
Topic on Project:Support desk
I doubt you will get an "official answer" here: Until we know for sure that MediaWiki is not affected, I would assume that it is. If MediaWiki is affected, this would be a security issue, which will not be published until it is fixed.
It is simple: PHP has a security update. If you use PHP, update it!