The default configuration of nginx, possibly 1.3.13 and earlier, uses world-readable permissions for the (1) access.log and (2) error.log files, which allows local users to obtain sensitive information by reading the files.
http://www.openwall.com/lists/oss-security/2013/02/24/1
http://www.openwall.com/lists/oss-security/2013/02/22/1
http://www.openwall.com/lists/oss-security/2013/02/21/15