Firefox Download from Command Line

Solved the same problem as follows, using Firefox:

• Open "Network" tab of "Web Developer" tool: Ctrl-Shift-E
• Visit the page you want to save (e.g. a photo behind a login)
• Right click the request and choose 'Copy'->'Copy as cURL'

This will give you a command that has all your cookie credentials e.g.

curl 'https://mysite.test/my-secure-dir/picture1.jpg' \ 
-H 'User-Agent: Mozilla/5.0 ...' \
-H 'Cookie: SESSIONID=abcdef1234567890'

You can modify the URL in the command to fetch whatever you want and run it in your shell.