/usr/share/php/Composer/Installer/ is in composer 1.6.3-1.
This file is owned by root:root, with mode 0o755.
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/usr/share/php/Composer/Installer/BinaryInstaller.php
/usr/share/php/Composer/Installer/BinaryPresenceInterface.php
/usr/share/php/Composer/Installer/InstallationManager.php
/usr/share/php/Composer/Installer/InstallerEvent.php
/usr/share/php/Composer/Installer/InstallerEvents.php
/usr/share/php/Composer/Installer/InstallerInterface.php
/usr/share/php/Composer/Installer/LibraryInstaller.php
/usr/share/php/Composer/Installer/MetapackageInstaller.php
/usr/share/php/Composer/Installer/NoopInstaller.php
/usr/share/php/Composer/Installer/PackageEvent.php
/usr/share/php/Composer/Installer/PackageEvents.php
/usr/share/php/Composer/Installer/PearBinaryInstaller.php
/usr/share/php/Composer/Installer/PearInstaller.php
/usr/share/php/Composer/Installer/PluginInstaller.php
/usr/share/php/Composer/Installer/ProjectInstaller.php
/usr/share/php/Composer/Installer/SuggestedPackagesReporter.php