Security issues fixed in Firefox 2.0.0.18
MFSA 2008-58 Parsing error in E4X default namespace
MFSA 2008-57 -moz-binding property bypasses security checks on codebase principals
MFSA 2008-56 nsXMLHttpRequest::NotifyEventListeners() same-origin violation
MFSA 2008-55 Crash and remote code execution in nsFrameManager
MFSA 2008-54 Buffer overflow in http-index-format parser
MFSA 2008-53 XSS and JavaScript privilege escalation via session restore
MFSA 2008-52 Crashes with evidence of memory corruption (rv:1.9.0.4/1.8.1.18)
MFSA 2008-50 Crash and remote code execution via __proto__ tampering
MFSA 2008-49 Arbitrary code execution via Flash Player dynamic module unloading
MFSA 2008-48 Image stealing via canvas and HTTP redirect
MFSA 2008-47 Information stealing via local shortcut files
Download Firefox 2
Note that Firefox 2.0.0.x maintenance is slated to end in mid-December, 2008. Version 2.0.0.19 is slated for release on December 16, 2008.
My copy of Firefox 2.0.0.17 was updated to 2.0.0.18 using the incremental update download with no obvious problems.
[Edited to add list of security fixes.]
UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.18) Gecko/20081029 Firefox/2.0.0.18



