Firefox 3.0.13, the update to the older browser that Mozilla will drop off the support list in January 2010, includes two bugs, while Firefox 3.5.2 fixes a separate flaw.
The vulnerabilities patched by Firefox 3.0.13 were disclosed last Thursday by Dan Kaminsky of IOActive and a security consultant who calls himself Moxie Marlinspike, at Black Hat in Las Vegas.
Independently, Kaminsky, best known as the discoverer of the , and Marlinspike demonstrated how in browsers' implementation of SSL (Secure Socket Layer), the Web's default encryption protocol.
Attackers could hijack a Web session to steal critical passwords or trick Firefox users into accepting a bogus software update that contained malware.
Firefox 3.5 was already safe from such attacks, since Mozilla's developers had used a newer, more secure version of NSS (Network Security Services), a set of code "libraries" for baking SSL into browsers.
That's why Firefox 3.5.2 patched only one vulnerability, a bug in how the browser handles replies from a SOCKS5 proxy. Mozilla rated the threat as "low" since it found no evidence of memory corruption, necessary to let hackers inject their own malicious code into the machine.
The SOCKS5 bug had been , which Mozilla issued July 21. It's unclear whether Mozilla simply forgot to patch the bug in Firefox 3.5.1, a fast-track update on July 16 to stymie a zero-day flaw, or if news of the SOCKS5 vulnerability reached Mozilla between Firefox 3.5.1 and 3.0.12.
Mozilla has shuttered access to the SOCKS5 flaw on its Bugzilla bug- and change-tracking database, so it's impossible to tell when the bug was logged. But because the (Common Vulnerabilities and Exposures) assigned to the vulnerability was activated July 15, either explanation is plausible.
Mozilla did not respond to a request for clarification Monday evening about whether it missed the SOCKS5 bug.
According to Web metrics company Net Applications, Firefox accounted for 22.5% of all browsers used worldwide during July. About Firefox users are still running 3.x, not the newer 3.5.
Firefox and can be downloaded for Windows, Mac OS X and Linux, but current users can also call up the browsers' updaters, or wait for automatic update notifications to appear in the next 48 hours.