A noted security researcher disclosed four new zero-day vulnerabilities in Microsoft and Mozilla's browsers, including a critical flaw in Internet Explorer (IE) and a major bug in Firefox.

Michael Zalewski, who regularly publishes browser flaw findings, posted details on the Full-disclosure mailing list for cookie-stealing, keystroke-snooping, malicious downloading and site-spoofing bugs

The full announcement is here:

http://seclists.org/fulldisclosure/2007/Jun/0026.html