[ Thanks to Mihai
Varzaru for this link. ]
“1. The problem
In Ubuntu gksu and sudo can be hijacked by an attacker who already
has access to the current non-administrative account. In order to
do that you can simply create a bin directory in your home folder,
add that directory to PATH and create in it the scripts: gksu and
sudo. The scripts would silently run any application the attacker
wants with root privileges and start the application you wanted to
start in the first place so that you won’t notice a thing.“So, after the attacker application (got on a website with a
firefox bug for example) gets access to your limited account all it
has to do in order to get root access is the above and wait for you
run something with administrative rights (like synaptic from the
menu; at some point even the updater which runs automatically was
calling gksu with a relative path).”