Firefox 3 cannot download files with white space in the filename

Question

When opening attachments in e-mail Firefox is unable to handle files with white space in the name. This is not the same as the white space file name truncation problem documented on this site (where file names with white space are truncated on saving.) The issue is that the browser will prompt to allow the file to be saved, but it will not prompt to open the file as an option. If I rename the file to remove white space then I do receive the "Open with..." dialog box. I verified that Firefox 2 did not have this problem and I can open attachments with white space in the file names just fine using that version of the browser (2.0.0.20).
== This happened ==
Every time Firefox opened
== Upgraded to version 3

Answer 1

When a user clicks on an attachment with spaces, the filename is truncated to the first whitespace. While IE, Chrome & Safari handle this, Firefox refuses to accept mime headers with unquoted filename parameters. According to Firefox's bugzilla/knowledgebase, Firefox's behavior is the correct behavior and it's a problem with most webservers or web applications. This problem can be easily corrected by surrounding the filename parameter with double quotes.
Eg.
Response.AddHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");