Warn about using bak_ as the database table name prefix. You should never use the bak_ database table name prefix on production sites. We have noticed some people who have accidentally done exactly that. Instead of creating a partial backup –since these database tables are automatically excluded– we will now display an error message with mitigation instructions and refuse to proceed with the backup.
Amazon S3: Support for ACLs on the uploaded backup archives. If you are using Amazon S3, or a compatible service, to store your backup archives, you can now choose which access control policy to use for the uploaded files. The default is Private which only allows access to the user uploading the file. If you are using IAM users to upload multiple sites' backups into the same bucket, you may want to set this to “Bucket owner has full control” to allow the owner (typically the root or a privileged user account) to be able to delete the backups.
Bug fixes and minor improvements.