Amazon Linux AMI Security Advisory: ALAS-2014-421
Advisory Release Date: 2014-10-01 18:52 Pacific
A virtual host confusion issue was found in nginx, allowing HTTPS connections for one origin to be redirected to the virtual host of a different origin. This leads to a variety of issues, such as cookie theft and session hijacking. It could be triggered from a cross-site scripting flaw, tricking a user into visiting a malicious URL, and so on.
Run yum update nginx to update your system.