The Mozilla Foundation has plugged a "critical" JavaScript vulnerability in the Firefox browser and the SeaMonkey application suite.

The patch, released Monday, targets Firefox versions 2.0.0.2 and 1.5.0.10, as well as SeaMonkey versions 1.1.1 and 1.0.8. An earlier fix for a JavaScript problem allowed scripts from web content to execute arbitrary code, Mozilla said in a security update.

The vulnerability allowed uniform resource identifiers in image tags to be executed even if JavaScript was disabled in the program preferences, Mozilla said. Disabling JavaScript does not protect against the flaw, so the foundation recommended that users upgrade to new versions.

Mozilla's Thunderbird email client was not affected by the vulnerability, it said.

The fix comes on the heels of the release of Firefox version 2.0.0.2, which fixed a handful of previously documented security problems.

Firefox has also come under criticism from independent researchers, including Polish vulnerability expert Michael Zalewski, regarding several other classes of vulnerabilities, some of which are related to new spoofing and phishing threats aimed at the software.

Window Snyder, chief security officer at Mozilla, said that her company is receiving more feedback than ever from customers concerned about browser security issues and promised that the firm is working hard to address any problems and set those fears at ease.

Because the browser is one of the most important applications on today's computers -- and a growing number of mobile devices -- it will likely remain a focal point for attacks and security researchers, but that comes with the territory, she said

Snyder believes that Mozilla is doing a better job than some of its competitors, such as Microsoft, in getting security patches out to users as quickly as possible. Whereas Microsoft typically follows a once-a-month pattern in releasing its patches, Mozilla is trying to fix problems as they emerge.

"It's important for us to focus on how quickly the fixes are made available, we try to focus on that and keep the window of risk as short as possible," Snyder said in a recent interview with InfoWorld.

"It's important to be flexible and dynamic to address these types of issues," said Snyder. "We've seen recent threats built to take advantage of Christmas or Valentine's Day, so, attackers don't work on our schedule, and we can't afford to look at it that way."

Industry analysts agreed that browser makers will need to remain vigilant about eliminating vulnerabilities and improving the overall security of their products as attackers continue to focus their own efforts on the applications.

Unlike other products that can be significantly bolstered for the sake of protecting against attacks, the very nature of browsers makes it much harder to limit potential weak points, said Dr. Chenxi Wang, an analyst with Forrester Research.

"The browser is of general use, it's not something specially-purposed that can be hardened, it has to be able to handle different types of sites and content, and it has to allow plug-ins," Wang said. "Browsers need to be secured more effectively, be they can't be put in a box as easily as with other specialised applications, because of all that, it will always be open to potential attacks."