According to Danish vulnerability tracker Secunia, Microsoft's Internet Explorer, Mozilla's Firefox, and virtually every other popular browser could be used by malicious Web site to display bogus Java dialog boxes atop legitimate sites.
Secunia has created a vulnerability test that users can quickly run to see if their browser is open to such a spoof.
Not only does the vulnerability exist in up-to-date editions of Internet Explorer, Firefox, Mozilla, Camino, Opera, and Safari, but it also affects the not-yet-released Firefox 1.0.5, which is in the last stages of testing.
"We expect a Firefox 1.0.5 release in the not too distant future," the quality control blog for Firefox read Tuesday. "We'd appreciate any help you all can offer by downloading and testing out these new bits."
It was expected that Firefox 1.0.5 would fix the frame insertion bug that crept back into the open-source browser's code, a gaffe that made news earlier in June.
Would 1.0.5 also fix this news flaw?
"We'll be taking a look at the vulnerability, and deciding whether it makes sense to put [a fix] in 1.0.5," said a Mozilla spokesman. "Firefox security is an ongoing process."
The spokesman wouldn't comment on whether any inclusion of a fix for the new vulnerability -- which Secunia rates as only a "less critical" threat -- would delay the appearance of 1.0.5, but said that the builds now available "were mostly for the development community. The release of 1.0.5 is a ways off."
Firefox 1.0.5 can be downloaded in its not-finished Windows, Mac, and Linux editions from the Mozilla Web site.