Firefox before 1.0 and Mozilla before 1.7.5 allows inactive (background) tabs to launch dialog boxes, which can allow remote attackers to spoof the dialog boxes from web sites in other windows and facilitate phishing attacks, aka the "Dialog Box Spoofing Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10211
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A100050
https://exchange.xforce.ibmcloud.com/vulnerabilities/18864
http://www.redhat.com/support/errata/RHSA-2005-335.html
http://www.redhat.com/support/errata/RHSA-2005-323.html
http://www.mozilla.org/security/announce/mfsa2005-05.html
http://secunia.com/multiple_browsers_form_field_focus_test/
http://secunia.com/multiple_browsers_dialog_box_spoofing_test/