/usr/share/doc/texlive-doc/otherformats/xmltex/base/testsec.tex is in texlive-htmlxml 2015.20160320-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | \def\xmlfile{testsec.xml}
\input xmltex.tex
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