Yes you have read that correctly. Microsoft posted a security update at the Microsoft Download Center yesterday for the recently released Service Pack 1 beta.
This update is needed to address one of the Patch Tuesday vulnerabilities that were patched on non SP1 beta Windows 7 64-bit systems.
A security issue has been identified that could allow an unauthenticated remote attacker to compromise your system and gain control over it. You can help protect your system by installing this update from Microsoft. After you install this update, you may have to restart your system.
So if you installed that SP1 Beta you need to install this update to stay secure while your testing.