/usr/share/php/HTMLPurifier/AttrDef/CSS/ is in php-htmlpurifier 4.7.0-1build1.
This file is owned by root:root, with mode 0o775.
..
/usr/share/php/HTMLPurifier/AttrDef/CSS/AlphaValue.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/Background.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/BackgroundPosition.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/Border.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/Color.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/Composite.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/DenyElementDecorator.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/Filter.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/Font.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/FontFamily.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/Ident.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/ImportantDecorator.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/Length.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/ListStyle.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/Multiple.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/Number.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/Percentage.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/TextDecoration.php
/usr/share/php/HTMLPurifier/AttrDef/CSS/URI.php