source: http://www.securityfocus.com/bid/15920/info

Round Cube will reportedly reveal its installation path in an error message output to the client. The filesystem layout can be sensitive information that is useful in other attacks against the target server. The trigger for this behavior is not clear; it may occur whenever a script fails and may be dependent on web-server or script configuration settings. 

Requesting this link:

http://xxxx.com/roundcube/?_auth=cf559dcf52d8801ccd51cd1f3ba3eca08d1b0bce= &_task=ma%60il

Caused this error message:

**PHP Error in /usr/local/apache2/htdocs/roundcube/index.php (301)*:* Invalid request failed/file not found