Details are unknown but in order for this exploit to work, you'll have to visit a site with the malicious code and click the infected link. Zero Day rates the severity as "High" and it effects both version 2 and 3 of the popular internet browser.
Mozilla has acknowledged the security issue and should have a patch issued in its 3.0.1 release shortly.
Don't click on the suspicious link.
Edited by Liskiller, 05 July 2008 - 07:33 PM.