Update your Firefox to 3.6.2

Mozilla has released Firefox 3.6.2 ... The update addresses some stability issues and a number of security vulnerabilities, most notably the critical security flaw described in Bug 552216, which could allow an attacker to execute malicious code on the target system.

http://www.pcworld.com/businesscenter/article/192149/firefox_update_addresses_critical_security_flaw.html