Mozilla Firefox 3.5.x before 3.5.11 and 3.6.x before 3.6.7, Thunderbird 3.0.x before 3.0.6 and 3.1.x before 3.1.1, and SeaMonkey before 2.0.6 permit cross-origin loading of CSS stylesheets even when the stylesheet download has an incorrect MIME type and the stylesheet document is malformed, which allows remote attackers to obtain sensitive information via a crafted document.
code.google.com/p/chromium/issues/detail?id=9877
scarybeastsecurity.blogspot.com/2009/12/generic-cross-browser-cross-domain.html
websec.sv.cmu.edu/css/css.pdf
www.mozilla.org/security/announce/2010/mfsa2010-46.html
bugzilla.mozilla.org/show_bug.cgi?id=524223
oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11811