Firefox before 1.0 and Mozilla before 1.7.5 allow remote attackers to obtain sensitive data from the clipboard via Javascript that generates a middle-click event on systems for which a middle-click performs a paste operation.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10362
https://exchange.xforce.ibmcloud.com/vulnerabilities/19171
https://bugzilla.mozilla.org/show_bug.cgi?id=265728
http://www.securityfocus.com/bid/12407
http://www.redhat.com/support/errata/RHSA-2005-384.html