core/string_api.php in Mantis before 1.1.3 does not check the privileges of the viewer before composing a link with issue data in the source anchor, which allows remote attackers to discover an issue's title and status via a request with a modified issue number.
http://www.securityfocus.com/bid/31868
http://www.openwall.com/lists/oss-security/2008/10/20/1
http://www.mantisbt.org/bugs/view.php?id=9321
http://www.mantisbt.org/bugs/changelog_page.php
http://www.gentoo.org/security/en/glsa/glsa-200812-07.xml
http://secunia.com/advisories/32975