Ubuntu Security Notice USN-261-1 – Stefan Esser discovered that the ‘session’ module did not sufficiently verify the validity of the user-supplied session ID. A remote attacker could exploit this to insert arbitrary HTTP headers into the response sent by the PHP application, which could lead to HTTP response splitting and cross site scripting attacks. PHP applications were also vulnerable to several cross site scripting flaws if the options ‘display_errors’ and ‘html_errors’ were enabled. Please note that enabling ‘html_errors’ is not recommended for production systems.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/44569/USN-261-1.txt
Source: https://packetstormsecurity.com/files/44569/Ubuntu-Security-Notice-261-1.html