Firefox Android adding random strings to attached file names

Firefox Android is adding '**tmp_random number-**' in prefix and '**-random number**' in suffix of the file name I attached to any website. I have tried Gmail and a number of website but it's changing my attached file name on all websites from 'Alam Resume.pdf' to 'tmp_123456-Alam Resume-1234567.pdf'. I have double checked the file name of the file in question and found it correct. I even tried attaching different files but the issue is still there but when I use desktop browser to send same files it didn't add any number to the attached file name. My Firefox Android version is 49.0.2 Android version is 5.1.1 Attaching files from ext SD Card