When using versioned media items that contain multiple versions, several versions can reference the same media file (BLOB) in the database. If a user attaches a new media file to a versioned media item, the system will remove the BLOB from the database, even if it is still referenced by other versions. This can cause data loss.
The same issue occurs if a user detaches a media file from a specific version of a versioned media item.
The issue does not affect unversioned media items. It also does not occur when you delete media items and move them to the recycle bin or archive.
A hotfix for Sitecore CMS 6.6.0 Update-3 is available on request.
To get the hotfix, please contact Sitecore Support via
http://support.sitecore.net (using reference number 380592 or 380433).