/usr/include/xsec/transformers/ is in libxml-security-c-dev 1.7.2-2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/xsec/transformers/TXFMBase.hpp
/usr/include/xsec/transformers/TXFMBase64.hpp
/usr/include/xsec/transformers/TXFMC14n.hpp
/usr/include/xsec/transformers/TXFMChain.hpp
/usr/include/xsec/transformers/TXFMCipher.hpp
/usr/include/xsec/transformers/TXFMConcatChains.hpp
/usr/include/xsec/transformers/TXFMDocObject.hpp
/usr/include/xsec/transformers/TXFMEnvelope.hpp
/usr/include/xsec/transformers/TXFMMD5.hpp
/usr/include/xsec/transformers/TXFMOutputFile.hpp
/usr/include/xsec/transformers/TXFMParser.hpp
/usr/include/xsec/transformers/TXFMSB.hpp
/usr/include/xsec/transformers/TXFMSHA1.hpp
/usr/include/xsec/transformers/TXFMURL.hpp
/usr/include/xsec/transformers/TXFMXPath.hpp
/usr/include/xsec/transformers/TXFMXPathFilter.hpp
/usr/include/xsec/transformers/TXFMXSL.hpp