Bear in mind, this isn't the

In reply to WINDOWS UPDATE breaks Quark, Corel, who knows what else?:

Bear in mind, this isn't the first Windows update to fix security bugs in its font-handling code, apparently it's just the first one to break functionality. And from what I can gather, this latest vulnerability affects TrueType fonts as well; the update only breaks OTF fonts since they typically use a different system rasterizer and API call. But the overall threat does seem more serious now that every major browser supports webfonts, so simply visiting a website could load a malicious font.