/usr/share/mediawiki-extensions/base/CategoryTree/ is in mediawiki-extensions-base 3.5~deb7u2.
This file is owned by root:root, with mode 0o755.
..
/usr/share/mediawiki-extensions/base/CategoryTree/CategoryPageSubclass.php
/usr/share/mediawiki-extensions/base/CategoryTree/CategoryTree.alias.php
/usr/share/mediawiki-extensions/base/CategoryTree/CategoryTree.css
/usr/share/mediawiki-extensions/base/CategoryTree/CategoryTree.i18n.magic.php
/usr/share/mediawiki-extensions/base/CategoryTree/CategoryTree.i18n.php
/usr/share/mediawiki-extensions/base/CategoryTree/CategoryTree.js
/usr/share/mediawiki-extensions/base/CategoryTree/CategoryTree.php
/usr/share/mediawiki-extensions/base/CategoryTree/CategoryTree.rtl.css
/usr/share/mediawiki-extensions/base/CategoryTree/CategoryTreeFunctions.php
/usr/share/mediawiki-extensions/base/CategoryTree/CategoryTreeIE.css
/usr/share/mediawiki-extensions/base/CategoryTree/CategoryTreePage.i18n.alias.php
/usr/share/mediawiki-extensions/base/CategoryTree/CategoryTreePage.php
/usr/share/mediawiki-extensions/base/CategoryTree/modules/
/usr/share/mediawiki-extensions/base/CategoryTree/modules/ext.categoryTree.css
/usr/share/mediawiki-extensions/base/CategoryTree/modules/ext.categoryTree.js