Hello, If for example you have set up unattended-upgrades and installed apt- listbugs, then when unattended-upgrades runs, apt-listbugs automatically pins (-30000) upgradable packages that are affected by bugs in order for them to be hold until a fix. They are automatically de-pinned when bugs are fixed. Such pinned packages appear in /etc/apt/preferences.d/apt-listbugs (look at apt-listbugs manpage for details)