This is absolutely ancient and fixed long ago
If you think this is ancient, read the official statement from Firefox
http://www.mozilla.org/security/history-title.html
"Unpatched Firefox 1.5 exploit made public" .
The way it affected me is becuase I leave my browser open and when I came back in the morning, it was chucking down 2GB of ram.
http://news.com.com/Unpatched+Firefox+1.5+exploit+made+public/2100-1002_3-5987401.html