source: https://www.securityfocus.com/bid/12686/info
 
Multiple remote input-validation vulnerabilities affect phpCOIN because the application fails to properly sanitize user-supplied input before using it to carry out critical functionality.
 
An attacker may leverage these issues to manipulate and view arbitrary database contents (by exploiting various SQL-injection issues) and to run arbitrary script code in the browser of an unsuspecting user (by exploiting multiple cross-site scripting vulnerabilities). 

http://www.example.com/phpcoin/login.php?w=user&o=login&e=u
%22%3E%3Cscript%3Edocument.write(document.cookie)%3C/script%3E