Greasemonkey before 0.3.5 allows remote web servers to (1) read arbitrary files via a GET request to a file:// URL in the GM_xmlhttpRequest API function, (2) list installed scripts using GM_scripts, or obtain sensitive information via (3) GM_setValue and GM_getValue.
https://exchange.xforce.ibmcloud.com/vulnerabilities/21453
http://www.vupen.com/english/advisories/2005/1147
http://secunia.com/advisories/16128
http://mozdev.org/pipermail/greasemonkey/2005-July/004022.html
http://greasemonkey.mozdev.org/changes/0.3.5.html
http://greaseblog.blogspot.com/2005/07/mandatory-greasemonkey-update.html