According to the release notes:
Firefox 1.0.7 is a security and stability release. We strongly recommend that all users upgrade to this latest version.
This version includes several security and stability fixes, including a fix for a reported buffer overflow vulnerability and a fix for a Linux shell command vulnerability.
On a sidenote. This is already the seventh iteration of Firefox in almost a year. On november 9th it will be exactly a year ago that Firefox went ‘public’. Already the browser has been downloaded 90 million times! So if you download/update there’s a chance you’ll contribute to make it to the 100 milllion download mark well before its anniversary.
Now, couldn’t November 9th 2005 be a more symbolic date to release Firefox 1.5?