• United States



by Dave Gradijan

Mozilla Fixes Firefox’s Security Flaws

Jun 05, 20073 mins
CSO and CISOData and Information Security

The Mozilla Foundation said last week it has patched several serious security flaws in the popular Firefox browser, bugs that also affect the SeaMonkey browser and the Thunderbird e-mail application.

The bugs could allow an attacker to take over a system, as well as less serious exploits such as spoofing or security bypass, Mozilla said.

While browser bug patches, even for critical flaws, have become somewhat routine, the latest alert highlights the fact that Firefox no longer has as clear an advantage over Microsoft’s Internet Explorer as it once did.

According to security firm Secunia, Firefox and IE 7 have been affected by a similar number of advisories so far this year, though IE has been hit by more serious bugs than Firefox.

In an advisory, Mozilla said the Firefox and update releases had fixed bugs that appeared to allow remote system access.

“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 company stated.

One bug involves Firefox’s JavaScript engine and could cause memory corruption and allow malicious code execution, Mozilla said.

The Thunderbird e-mail client uses Firefox’s browser engine and is thus also vulnerable. However, since JavaScript is disabled by default in Thunderbird, users are unlikely to be affected, the company said.

“We strongly discourage users from running JavaScript in mail,” the company said. The advisory added that it may be possible to exploit the memory corruption vulnerability through some means other than JavaScript, such as large images.

Also fixed were an error in the “addEventListener” method, which could be exploited to inject script from one site into another, and a bug in the handling of XUL pop-ups that could allow spoofing of the location bar or other browser interface components.

Secunia called the bugs “highly critical.”

To date, Firefox has been affected by five vulnerabilities and IE 7 by six, according to Secunia’s statistics.

Forty percent of the Firefox bugs remain unpatched, compared with 50 percent for IE 7. But only 13 percent of the Firefox bugs allowed system access, compared to 43 percent for IE 7, which is more closely integrated with Windows.

Correspondingly, Secunia ranked 17 percent of the IE bugs as “extremely critical,” a status attained by none of the Firefox advisories.

Forty percent of the Firefox advisories were “highly critical,” with the rest less serious. Along with IE 7’s 17 percent “extremely critical” bugs, 33 percent were “highly critical” and the others were less serious.

—Matthew Broersma,