Today Mozilla began pushing Firefox 16.0.1 as an emergency update for Mac and other operating systems that fixes four critical vulnerabilities. The discovery of a critical bug, which the company said “could allow a malicious site to potentially determine which websites users have visited and have access to the URL or URL parameters,” prompted Mozilla to pull Firefox 16 from distribution on Wednesday while working to resolve the issue.
Although the vulnerability is now fixed in Firefox 16.0.1, security researcher Gareth Heyes missed out on a $3,000 bug bounty after blogging about the Firefox 16 only symptom before Mozilla was able to fix it. In addition to the critical vulnerability and other security flaws related to arbitrary code execution, Mozilla developers identified and fixed two top crashing bugs in the browser engine used in Firefox.
Described in the security advisory MFSA 2012-88:
These bugs 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.
The first of these bugs, a FreeType issue, is a mobile only issue which happens on custom kernels like Cyanogenmod, not on standard Android installations. The second bug is a websockets crash affecting Firefox 16 but not Firefox ESR.
We recommend downloading Firefox 16.0.1 from Mozilla's official site, or you can use the program's built-in auto-updater (Firefox > About Firefox > Check for Updates).