The filename parameter of the Context.FileAttachment function is not properly sanitized. A maliciously crafted filename can cause the Content-Disposition header to be sent with an unexpected filename value or otherwise modify the Content-Disposition header. For example, a filename of "setup.bat";x=.txt" will be sent as a file named "setup.bat".
If the FileAttachment function is called with names provided by an untrusted source, this may permit an attacker to cause a file to be served with a name different than provided. Maliciously crafted attachment file name can modify the Content-Disposition header.