An unpatched critical security vulnerability in Microsoft's software is being actively exploited by cybercriminals.
The exploit allows what's known as a drive-by install: you can become infected simply by visiting a website with Internet Explorer.
Alongside last week's regular Patch Tuesday announcement (including a remote code execution vulnerability that is being exploited by attackers in the wild), Microsoft also issued an out-of-band security advisory about an as-yet unpatched security hole (known as CVE-2012-1889).
Read more: http://nakedsecurity.sophos.com/2012/06/19/unpatched-microsoft-security-vulnerability-exploited/