Some software might, for example, modify the firewall and break the security built in Tails. But other software like games or office tools are probably fine.
Software not [[officially included in Tails|doc/about/features]] might have not been tested for security.We also cannot provide support or documentation for it.
<p>Configuring additional APT repositories might break the security built in Tails and might install software that has not even been approved by Debian. Be even more careful with what you install.</p>