Happens when trying to attach an image with a filename containing a slash(/)
File names should not have slashes in them, they're not valid file names - one slash indicates "directory" not a file name and the other indicates control characters.
But it is bug that you get an internal server error instead of a bad file name message.
Rename the file to a valid name and try again.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.