all .html are not blocked AFAIK!
when the upload filter mask is empty, this is what's actually used
\hfs.*;index.htm*;default.htm*;descript.ion;*.md5
the initial slash is actually inverting the logic, so those files are NOT allowed.
would you enter "*", anything could be uploaded.
anyway my suggestion is that, for security reasons, you enter the mask i just gave you but modified for your needs.