Only hours after Mozilla launched the final of Firefox 3.0, a researcher sold a critical vulnerability in the browser to TippingPoint's bug bounty program, the security company acknowledged Wedesday.

The bug has been reported to Mozilla, TippingPoint announced in a post to a company blog. "While Mozilla is working on a fix, we won't be divulging anything else until a patch is available," said TippingPoint, citing policy. "Once the issue is patched, we'll be publishing an advisory."

The Austin, Tex.-based security vendor operates the Zero Day Initiative (ZDI), one of two prominent vulnerability purchasing programs, and regularly buys bugs from independent researchers, then reports the flaws to the appropriate vendor. It's perhaps best known for sponsoring an annual hacking contest, in which researchers try to break into stock Windows, Mac OS X or Linux laptops, at the annual CanSecWest security conference.

TippingPoint released little information about the Firefox bug other than to confirm that it affects the new Firefox 3.0 as well as older 2.0 versions. TippingPoint classified the vulnerability as "critical" and said it could be used to execute remote code. There is one caveat, however, said TippingPoint. "Not unlike most browser-based vulnerabilities that we see these days, user interaction is required, such as clicking on a link in e-mail or visiting a malicious Web page."

The company didn't hint whether the vulnerability was present in all editions of Firefox 3.0, or was specific to one operating system. However, it hinted that a patch might come quickly. "Working with Mozilla on past security issues, we've found them to have a good track record and expect a reasonable turnaround on this issue as well," said TippingPoint.

Mozilla regularly touts its patch speed when it defends its security record. Last January, for instance, Window Snyder, the open-source vendor's chief security executive, rebutted a news report that claimed Firefox was less secure than Microsoft's Internet Explorer by noting that Mozilla patches faster than Microsoft. "At Mozilla we work as hard as we can to ship fixes as soon as possible to minimize the exposure to our users," she said then in a post to the company's security blog.

Mozilla was not available late Wednesday for comment or to answer questions.

Firefox 3.0, released Tuesday, was downloaded more than 8.3 million times in its first 24 hours of availability.

(Read Firefox 3.0 review here).