Although Google's Chrome was the only browser left standing after March's Pwn2Own hacking contest, it was vulnerable to the same bug that a German college student used to bring down Apple's Safari, Google acknowledged this week.
Although Google patched the Chrome vulnerability May 7, it waited until last Wednesday to reveal that the bug was the same WebKit flaw that Apple patched the day before.
"[We are] disclosing that this release contains the fix for CVE-2009-0945, an issue in WebKit code that also affects Apple's Safari," Mark Larson, the program manager for Chrome, said in a May 13 post.
"We did not want to disclose this until Apple's fix for Safari users was released."
Apple patched the WebKit vulnerability Tuesday as part of a massive security update for both Mac OS X 10.5, aka Leopard, and Mac OS X 10.4, or Tiger.
Last March, Nils, a German computer science student who would give only his first name, hacked three browsers in quick succession -- a then-unfinished version of Internet Explorer 8 (IE8), Firefox and Safari -- at the Pwn2Own challenge, walking away with $15,000 in cash. Chrome was the only browser up for grabs that Nils didn't break.
Chrome and Safari both rely on the open-source WebKit rendering engine to power their browsers.
According to Larson, the bug is in WebKit's handling of SVGList objects, and could be exploited by hackers able to dupe users into visiting a malicious site. But because Chrome runs in a "sandbox," a security technology that blocks access to the system, even if a hacker managed to hijack the browser, he could only run attack code in that sandbox surrounding the browser. Microsoft's IE7 and IE8, when running on Vista or Windows 7, offer a similar defense.
Chrome's bug database first noted the vulnerability March 19, the same day Nils hacked IE8, Firefox and Safari. By the next day, developers were talking about keeping the bug under wraps.
"Apple wants to carefully coordinate disclosure because this bug has a high profile," wrote one developer, identified only as "abarth" on the database thread. "Apple is also concerned about patches appearing in public source trees." Chrome developers had a patch ready by March 22.
Mozilla patched the Firefox flaw Nils exploited on March 27, while Microsoft's final build of IE8, which was released shortly after the contest, was safe from Nils' hack when run in Vista SP1 or Windows 7. Microsoft has not, however, actually patched IE8 or IE7; some believe the latter is also vulnerable to Nils' exploit.
Google automatically updates Chrome behind the scenes, so users running the so-called "stable" builds need take no additional action.