Firefox before 1.0 allows the user to store a (1) javascript: or (2) data: URLs as a Livefeed bookmark, then executes it in the security context of the currently loaded page when the user later accesses the bookmark, which could allow remote attackers to execute arbitrary code.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A100046
https://exchange.xforce.ibmcloud.com/vulnerabilities/19187
https://bugzilla.mozilla.org/show_bug.cgi?id=265668