Adobe Labs has released another update to Lightroom bringing it to version 4.1 RC 2. The new release supports new cameras, adds a new Defringe Control to help address chromatic aberration, and now can read 16-bit, 24-bit, and 32-bit HDR files. You can read more about the details here and download the update here.
A Release Candidate is a pre-release of the update to get user feedback and make sure it works all right before the official release.
The new Defringe control is available in the Lens Correction panel in the Color section. If you want to read the details on how to use this new feature you can read the technical sheet at Adobe's website here.