The most popular series of custom ROM’s has received yet another major update. CyanogenMod v7.0.3 and v126.96.36.199 depending on the device, include a very important security fix. The CyanogenMod team highly recommends the update for any user currently running versions 7.0 7.0.2 or 188.8.131.52 releases. There is a catch, if you are currently using a cm7.1 nightly build, do NOT update to v7.0.3.* as the fixes are already included in any build after May 4th. Downgrading from a v7.1 nightly build (Android v2.3.4) to a v7.0.* stable release (Android v2.3.3) is known to cause issues. The update to v7.0.3.* also includes a bug fix for the notification system.
Source: CyanogenMod Blog