I have heard from a couple of people who are real concerned about security, that they wanted sandbox to not only delete the content but to "shred" it on exit.
policycoreutils-2.1.13-17.fc18
policycoreutils-2.1.13-17.el7
man shred
...
DESCRIPTION
Overwrite the specified FILE(s) repeatedly, in order to make it harder
for even very expensive hardware probing to recover the data.
cat untrustedcontent | sandbox --shred sandbox -M filter.sh > /tmp/trustedcontent
or
sandbox -X -s -W metacity firefox
