From saltyho...@gmail.com on September 01, 2009 20:07:10

Some badly-made ePub archives contain useless metadata files such as
Thumbs.db or even "backup" zip files of the archive.
They can add to the ePub file size quite a bit.

Perhaps epubcheck could specifically check for Thumbs.db or, more
generally, warn about files that aren't in the manifest.

Original issue: http://code.google.com/p/epubcheck/issues/detail?id=38