Mozilla, the non-profit group behind the Firefox opensource browser, has issued an alert, warning users that a combination of bugs could allow criminals to access users' private information - including banking details, logins and passwords.

There is broad concern that hackers may be turning their focus on Firefox, which initially won over users by promising more secure internet surfing.

The exploitation of two separate flaws in Firefox means that outside hackers can return to surfers’ previously visited pages. These could contain credit card details or other personal information.

The rush to patch the problems, which also affect Mozilla Suite, the all-in-one internet application, marked the fourth major security scare at Mozilla in three months.

Firefox users have been urged to disable the browser's javascript option to provide a temporary fix to the problem.

Mozilla has also recommended that the browser's software installation feature be disabled.

This can be done by unchecking the "Allow web sites to install software" box, which can be found by selecting "Options" on the "Tools" menu and then "Web Features".

Further instructions on how to do carry out these measures can be found at http://www.mozilla.org/security/announce/mfsa2005-42.html.

Industry figures suggest that Firefox has built a significant user base with some websites claiming more that Firefox has overtaken Internet Explorer, Microsoft's market leading browser. Around 15 per cent of Times Online's readers use the Mozilla browser.

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