PDFium, as used in Google Chrome before 47.0.2526.73, does not properly restrict use of chrome: URLs, which allows remote attackers to bypass intended scheme restrictions via a crafted PDF document, as demonstrated by a document with a link to a chrome://settings URL.
https://security.gentoo.org/glsa/201603-09
https://codereview.chromium.org/1362433002
https://code.google.com/p/chromium/issues/detail?id=528505
http://www.securitytracker.com/id/1034298
http://www.securityfocus.com/bid/78416
http://www.debian.org/security/2015/dsa-3415
http://lists.opensuse.org/opensuse-security-announce/2015-12/msg00017.html
http://lists.opensuse.org/opensuse-security-announce/2015-12/msg00016.html
http://googlechromereleases.blogspot.com/2015/12/stable-channel-update.html