The CSSLoaderImpl::DoSheetComplete function in layout/style/nsCSSLoader.cpp
in Mozilla Firefox 3.0.x before 3.0.18, 3.5.x before 3.5.8, and 3.6.x
before 3.6.2; Thunderbird before 3.0.2; and SeaMonkey before 2.0.3 changes
the case of certain strings in a stylesheet before adding this stylesheet
to the XUL cache, which might allow remote attackers to modify the
browser's font and other CSS attributes, and potentially disrupt rendering
of a web page, by forcing the browser to perform this erroneous stylesheet
caching.

chriscoulson