AppServ Open Project 'appservlang' Cross-site Scripting Vulnerability

Summary
This host is running AppServ Open Project and is prone to cross site scripting vulnerability.
Impact
Successful exploitation will allow remote attackers to execute arbitrary HTML and script code in a user's browser session in the context of an affected application. Impact Level: Application
Solution
No solution or patch was made available for at least one year since disclosure of this vulnerability. Likely none will be provided anymore. General solution options are to upgrade to a newer release, disable respective features, remove the product or replace the product by another one.
Insight
The flaw is due to an input passed to the 'appservlang' parameter in 'index.php' is not properly sanitised before being returned to the user.
Affected
AppServ Open Project Version 2.5.10 and prior