<p>The packages included in Tails are carefully tested for security. Installing additional packages might break the security built into Tails. For example, installing OpenVPN might modify the firewall rules that Tails uses to force network traffic to go through Tor.</p>
<p>Configuring additional APT repositories might break the security built into Tails and might install software that has not even been approved by Debian. Be even more careful with what you install.</p>