Mozilla just released Firefox 3.0.7 that fixes a variety of security and stability issues as well as bugs.
MFSA 2009-11 URL spoofing with invisible control characters
Certain invisible control characters were being decoded when displayed in the location bar, resulting in fewer visible characters than were present in the actual location. An attacker could use this vulnerability to spoof the location bar and display a misleading URL for their malicious web page.
MFSA 2009-10 Upgrade PNG library to fix memory safety hazards
Several memory safety hazards were identified in PNG libraries used by Mozilla. These vulnerabilities could be used by a malicious website to crash a victim’s browser and potentially execute arbitrary code on their computer. libpng was upgraded to a version which contained fixes for these flaws.
MFSA 2009-09 XML data theft via RDFXMLDataSource and cross-domain redirect
A website could use nsIRDFService and a cross-domain redirect to steal arbitrary XML data from another domain, a violation of the same-origin policy. This vulnerability could be used by a malicious website to steal private data from users authenticated to the redirected website.
MFSA 2009-08 Mozilla Firefox XUL Linked Clones Double Free Vulnerability
A vulnerability was discovered in Mozilla’s garbage collection process. The vulnerability was caused by improper memory management of a set of cloned XUL DOM elements which were linked as a parent and child. After reloading the browser on a page with such linked elements, the browser would crash when attempting to access an object which was already destroyed. An attacker could use this crash to run arbitrary code on the victim’s computer.
MFSA 2009-07 Crashes with evidence of memory corruption (rv:18.104.22.168)
Mozilla developers identified and fixed several stability bugs in the browser engine used in Firefox and other Mozilla-based products. Some of these crashes showed evidence of memory corruption under certain circumstances and we presume that with enough effort at least some of these could be exploited to run arbitrary code.