A flaw was found in the way Firefox displays the autocomplete popup. Malicious content could use this flaw to steal form history information.
This is now public: http://www.mozilla.org/security/announce/2011/mfsa2011-14.html
This issue has been addressed in following products: Red Hat Enterprise Linux 5 Red Hat Enterprise Linux 6 Red Hat Enterprise Linux 4 Via RHSA-2011:0471 https://rhn.redhat.com/errata/RHSA-2011-0471.html