/usr/share/php/Monolog/Processor/ is in php-monolog 1.23.0-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/php/Monolog/Processor/GitProcessor.php
/usr/share/php/Monolog/Processor/IntrospectionProcessor.php
/usr/share/php/Monolog/Processor/MemoryPeakUsageProcessor.php
/usr/share/php/Monolog/Processor/MemoryProcessor.php
/usr/share/php/Monolog/Processor/MemoryUsageProcessor.php
/usr/share/php/Monolog/Processor/MercurialProcessor.php
/usr/share/php/Monolog/Processor/ProcessIdProcessor.php
/usr/share/php/Monolog/Processor/PsrLogMessageProcessor.php
/usr/share/php/Monolog/Processor/TagProcessor.php
/usr/share/php/Monolog/Processor/UidProcessor.php
/usr/share/php/Monolog/Processor/WebProcessor.php