/usr/lib/slepcdir/3.4.2/index.html is in slepc3.4.2-doc 3.4.2.dfsg-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/slepcdir/3.4.2/../../../share/doc/slepc3.4.2-doc/docs/index.html
/usr/lib/slepcdir/3.4.2/../../../share/doc/slepc3.4.2-doc/docs/index.html