Best Practical Solutions RT 3.8.x before 3.8.15 and 4.0.x before 4.0.8, when GnuPG is enabled, allows remote attackers to bypass intended restrictions on reading keys in the product's keyring, and trigger outbound e-mail messages signed by an arbitrary stored secret key, by leveraging a UI e-mail signing privilege.
http://lists.bestpractical.com/pipermail/rt-announce/2012-October/000212.html