phpCOIN v1.6.5 was released on 2009-09-26. It adds some minor new functionality, changes some functionality, and addresses several outstanding issues.
Users wishing to deploy this version on a PHP 5.3.x platform should read This forum post
Critical Security Announcement
A vulnerability in the way that input passed to phpCOIN is sanitized has been discovered.After installing this version, users should apply the HotFix as instructed at http://forums.phpcoin.com/index.php?showtopic=3223 as soon as possible