The "Open 'safe' files after downloading" option in Safari on Apple Mac OS X allows remote user-assisted attackers to execute arbitrary commands by tricking a user into downloading a __MACOSX folder that contains metadata (resource fork) that invokes the Terminal, which automatically interprets the script using bash, as demonstrated using a ZIP file that contains a script with a safe file extension.
https://exchange.xforce.ibmcloud.com/vulnerabilities/24808
http://www.vupen.com/english/advisories/2006/0671
http://www.us-cert.gov/cas/techalerts/TA06-062A.html
http://www.us-cert.gov/cas/techalerts/TA06-053A.html
http://www.mathematik.uni-ulm.de/numerik/staff/lehn/macosx.html
http://www.kb.cert.org/vuls/id/999708
http://www.heise.de/english/newsticker/news/69862