Mozilla on Wednesday patched 10 security vulnerabilities in Firefox 3.5, all but one ranked critical, as it delivered the first update that automatically checks for outdated versions of the popular Flash Player plug-in.
In four separate sets of patches, Firefox 3.5.3 fixed a total of 10 flaws, the majority of them stability issues in the application's browser and JavaScript rendering engines, some of which Mozilla said might be exploitable by hackers.
Four of the seven vulnerabilites outlined in the MFSA 2009-47 advisory produce browser engine crashes, while the other three crash Firefox's new TraceMonkey JavaScript engine.
"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," the advisory acknowledged, using boilerplate language Mozilla often uses to describe critical bugs.
Mozilla recommended that users disable JavaScript in Firefox if they were unable or unwilling to patch the browser.
Three other advisories spelled out critical vulnerabilites in Firefox's RSS function and in Mozilla's XML-based language, XUL (XML User Interface Language), which is used to create Web applications able to operate offline; and a URL-spoofing bug the company ranked as "low," the least dangerous of the firm's four-step scoring system.
Only two of the 10 vulnerabilities were uncovered by outside researchers; Mozilla's own developers or security engineers rooted out the rest. One of the two reported by outsiders came from 3Com TippingPoint's Zero Day Initiative, a bounty program that pays people for turning in bugs.
Mozilla also patched the 2008 edition of Firefox on Wednesday, updating that version to 3.0.14 as it fixed 11 flaws, only one of which was unique to the older edition.
That vulnerability, said Mozilla in the accompanying advisory , could be used by attackers to trick a user into installing a malicious security module in the browser. Mozilla ranked the bug as a "moderate" threat.
According to Mozilla, Dan Kaminsky of IOActive, a researcher best known as the discoverer of the DNS vulnerability in July 2008, reported that Firefox 3.0 remains vulnerable to possible remote attacks using malicious security modules.
Kaminsky's research was also involved in a pair of patches that Mozilla rolled out last month for Firefox.
The clock is ticking on Firefox 3.0. Mozilla will provide security updates for the 15-month-old browser only until January 2010.
Wednesday's updates kicked off a new Mozilla plan to check for outdated plug-ins that are popular with both users and attackers.
After Firefox is updated to 3.5.3 or 3.0.14, the new browser detects the Flash Player plug-in if it's present, then warns users if it's not the most up-to-date edition.
Mozilla wants to expand the plug-in check in Firefox 3.6, which is currently set to ship in November, to detect outdated versions of Apple's QuickTime; Adobe's Flash, Shockwave and Reader; Microsoft's Silverlight; and Sun's Java.
Firefox 3.5.3 and 3.0.14 can be downloaded for Windows, Mac OS X and Linux, but current users can also call up the browsers' updater tools, or wait for automatic update notifications to appear in the next 48 hours.