Firefox 1.0.7 and previous versions have a potential exploit floating around now, in the form of denial of service. Although the exploit does not cause your system to become compromised or otherwise be at risk for other forms of attack it could end up being quite a nuisance and as such we hope it gets patched soon. Mozilla has been on top of things in the past and likely we will see an update for the software son. The Deer Park beta versions of Firefox (1.5 beta 2) are not vulnerable to this, so you may consider switching to the beta. Anyone using Firefox will likely get a notification of the patch once it becomes available.