source: https://www.securityfocus.com/bid/10246/info

It has been reported that SquirrelMail is affected by a cross-site scripting vulnerability in the handling of folder name displays. This issue is due to a failure of the application to properly sanitize user-supplied input prior to including it in dynamic web content.

This issue may allow for theft of cookie-based authentication credentials. Other attacks are also possible.

http://www.example.com/mail/src/compose.php?mailbox="><script>window.alert(document.cookie)</script>