Race condition in GNU nano before 2.2.4, when run by root to edit a file that is not owned by root, allows local user-assisted attackers to change the ownership of arbitrary files via vectors related to the creation of backup files.
http://drosenbe.blogspot.com/2010/03/nano-as-root.html
http://lists.gnu.org/archive/html/nano-devel/2010-04/msg00000.html
http://secunia.com/advisories/39444
http://svn.savannah.gnu.org/viewvc/trunk/nano/ChangeLog?revision=4503&root=nano&view=markup