There's been a fair bit of static regarding the IDN Buffer Overflow flaw in Firefox recently. The fix is available here, but it's really a workaround as it just disables International Domain Name support (i.e. non-English, local language characters in URLs) which is not much help for those of us that need to access such sites.
It's been a bit of a contentious issue, as the bloke that discovered the flaw announced it publicly almost immediately, having had some kind of altercation with Mozilla. In my book, that's a bit naughty really, as he should have given Mozilla a chance to produce a patch before it became public knowledge. Still, it'll be fixed in the next version.