/usr/share/doc/r-doc-html/manual/R-exts.html is in r-doc-html 3.3.3-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/r-doc-html/manual/../../../R/doc/manual/R-exts.html
/usr/share/doc/r-doc-html/manual/../../../R/doc/manual/R-exts.html