The safe-level feature in Ruby 1.8.6 through 1.8.6-420, 1.8.7 through 1.8.7-330, and 1.8.8dev allows context-dependent attackers to modify strings via the Exception#to_s method, as demonstrated by changing an intended pathname.
http://lists.apple.com/archives/security-announce/2012/May/msg00001.html
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/054422.html
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/054436.html
http://secunia.com/advisories/43420
http://secunia.com/advisories/43573
http://support.apple.com/kb/HT5281
http://www.mandriva.com/security/advisories?name=MDVSA-2011:097
http://www.mandriva.com/security/advisories?name=MDVSA-2011:098
http://www.openwall.com/lists/oss-security/2011/02/21/2
http://www.openwall.com/lists/oss-security/2011/02/21/5
http://www.redhat.com/support/errata/RHSA-2011-0908.html
http://www.redhat.com/support/errata/RHSA-2011-0909.html
http://www.redhat.com/support/errata/RHSA-2011-0910.html
http://www.ruby-lang.org/en/news/2011/02/18/exception-methods-can-bypass-safe/
http://www.securityfocus.com/bid/46458