i set the upload type question and upload the gif picture.
but when you download the file,the file name is changed to fu_yyf7emtckam54k5, and the file type is not gif.
what's the problem?

There is no problem. The file name has been obfuscated and the extension removed for security reasons.

extension means nothing in linux, i am not sure what's the security reason.
then, the problem is how to use the file after download if without extension??