Fedora 18, Firefox, and local STIX fonts

This was first reported on g+.

There is an odd bug on Fedora 18 with Firefox (reported for FF21, confirmed on a fresh install with FF17). The HTML-CSS output is quite broken (see screenshots above, but all kinds of buggy stuff shows up).

Fedora 18 comes with STIX fonts installed (though there's also a stix-math-fonts package whose installations did not help). The MathJax about page states that local STIX fonts are used.

I'm guessing something goes wrong in the font detection. For comparison, Chromium 27 went straight to webfonts.

As a workaround for Firefox, installing Fred's mathml-fonts extension resolves the issues (as does removing the STIX fonts -- the MathJax webfonts work fine).