BUG: XLS detected as DOC

In my application, I need to be able to handle various different types of documents. I have a method which goes through many steps to determine what type of document I am dealing with. In the first step, it uses Document.DetectFileFormat to determine if the document is supported by Words. If it is, it loads it. If not, it checks if it is supported by Cells.
When I tested this with a Word document, it works great. Even if I use a non-supported document (by either Cells or Words) it works fine. If I test it with an Excel document, however, the DetectFileFormat method flags this as being a Doc and my code tries to load it. This is unacceptable.
Am I doing something wrong here? Xls is not a Doc. Hopefully this can be fixed in short order. For now I will rearrange my code to attempt to load it as an Excel document first. Hopefully, Cells doesn’t try to load the Word document.

Thanks for your request. This is known issue #4800. We will try to resolve this issue before the next release (within 3-4 weeks). I will notify you as soon as it is fixed.
As a workaround you can also check extension.
Best regards

The issues you have found earlier (filed as 4800) have been fixed in this update.