/usr/share/icingaweb2/modules/doc/library/ is in icingaweb2-module-doc 2.1.0-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/icingaweb2/modules/doc/library/Doc/
/usr/share/icingaweb2/modules/doc/library/Doc/DocController.php
/usr/share/icingaweb2/modules/doc/library/Doc/DocIterator.php
/usr/share/icingaweb2/modules/doc/library/Doc/DocParser.php
/usr/share/icingaweb2/modules/doc/library/Doc/DocSection.php
/usr/share/icingaweb2/modules/doc/library/Doc/DocSectionFilterIterator.php
/usr/share/icingaweb2/modules/doc/library/Doc/Exception/
/usr/share/icingaweb2/modules/doc/library/Doc/Exception/ChapterNotFoundException.php
/usr/share/icingaweb2/modules/doc/library/Doc/Exception/DocEmptyException.php
/usr/share/icingaweb2/modules/doc/library/Doc/Exception/DocException.php
/usr/share/icingaweb2/modules/doc/library/Doc/Renderer/
/usr/share/icingaweb2/modules/doc/library/Doc/Renderer/DocRenderer.php
/usr/share/icingaweb2/modules/doc/library/Doc/Renderer/DocSearchRenderer.php
/usr/share/icingaweb2/modules/doc/library/Doc/Renderer/DocSectionRenderer.php
/usr/share/icingaweb2/modules/doc/library/Doc/Renderer/DocTocRenderer.php
/usr/share/icingaweb2/modules/doc/library/Doc/Search/
/usr/share/icingaweb2/modules/doc/library/Doc/Search/DocSearch.php
/usr/share/icingaweb2/modules/doc/library/Doc/Search/DocSearchIterator.php
/usr/share/icingaweb2/modules/doc/library/Doc/Search/DocSearchMatch.php