Microsoft today shipped patches for at least 11 documented security vulnerabilities, including one that's already being hit with "limited, targeted attacks."

The vulnerability under attack -- now fixed today with the MS12-027 bulletin -- exists in Windows Common Controls and can be exploited to launch remote code execution attacks if a user simply surfs to a malicious website.

The vulnerability is caused when the MSCOMCTL.OCX ActiveX control, while being used in Internet Explorer, corrupts the system state in such a way as to allow an attacker to execute arbitrary code.

Microsoft is calling on Windows users to apply this bulletin as a priority because of the high-risk of code execution attacks.

The company is also calling special attention to MS12-023, which addresses at least 5 flaws in the Internet Explorer browser.

The most severe vulnerabilities could allow remote code execution if a user views a specially crafted webpage using Internet Explorer. An attacker who successfully exploited any of these vulnerabilities could gain the same user rights as the current user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

Windows users are also urged to apply a third "critical" bulletin (MS12-024), which covers a "critical" vulnerability that allows remote code execution if a user or application runs or installs a specially crafted, signed portable executable (PE) file on an affected system.

This month's Patch Tuesday batch also includes: