Running firefox a bit more safely - HOWTO

[Carsten Mattner]

On Tue, Aug 11, 2015 at 7:32 PM, Matthew Dillon
<dillon at apollo.backplane.com> wrote:
>         #!/bin/csh
>         #
>         # script for ~/bin/firefox  (assumes ~/bin is in your path)
>         #
>         scp ~/.Xauthority dfw1 at localhost:
>         ssh dfw1 at localhost -n "setenv DISPLAY :0.0; firefox"

snip

>     * Also note that these applications will be able to use X shared memory
>       and thus run fairly optimally (they are NOT using an ssh tunnel nor do
>       we want them to as that would be ridiculously slow).  Programs run in
>       this way will not have direct access to the GPU so 3D might not be
>       so hot.  But for general browsing I haven't had any trouble, and even
>       with 4K video appears to work about the same as it did before.

Can you explain how this works without going through localhost:22?
Isn't X forwarded through the ssh tunnel?