A second minor bug found in the Firefox 2.0 browser will be fixed, but users shouldn't encounter much of a problem in the mean time, a Mozilla official has said.

The browser will crash if it visits a Web page that been intentionally coded with JavaScript in such a way as to target the bug, said Tristan Nitot, director of European operations for Mozilla.

"It's very unlikely that anyone would have put a similar page on any ordinary Web page," so users shouldn't be affected, Nitot said.

The problem can't be used to steal data from a computer, he added.

It's the second bug that's been found in Firefox 2.0 since its release on 24 October. The first bug also causes the browser to hang or crash when a very large document is loaded into an iframe - an HTML element - using JavaScript.

The new bug will eventually be fixed. "We will fix it because we need reliability," Nitot said, adding no timetable has been set.

Firefox 2.0 and Microsoft's rival Web browser Internet Explorer 7 (IE7), both of which debuted within a week of one another, are under close scrutiny by security analysts.

Both vendors have contested experts' claims of flaws. Mozilla said one reported problem with Firefox 2.0 was fixed in a previous version, while a second report of an exploitable vulnerability couldn't be replicated.

Microsoft charged that a behaviour cited as a vulnerability in IE7 - where a pop-up window can display content from a different, untrusted Web site - isn't a bug, but a feature after the behaviour was reported by vendor Secunia AsP.