/usr/share/xul-ext/ is in xul-ext-openinbrowser 1.15-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/xul-ext/openinbrowser/
/usr/share/xul-ext/openinbrowser/chrome/
/usr/share/xul-ext/openinbrowser/chrome.manifest
/usr/share/xul-ext/openinbrowser/chrome/content/
/usr/share/xul-ext/openinbrowser/chrome/content/browserOverlay.js
/usr/share/xul-ext/openinbrowser/chrome/content/browserOverlay.xul
/usr/share/xul-ext/openinbrowser/chrome/content/openInBrowser.js
/usr/share/xul-ext/openinbrowser/chrome/content/unknownContentTypeOverlay.js
/usr/share/xul-ext/openinbrowser/chrome/content/unknownContentTypeOverlay.xul
/usr/share/xul-ext/openinbrowser/chrome/locale/
/usr/share/xul-ext/openinbrowser/chrome/locale/de-DE/
/usr/share/xul-ext/openinbrowser/chrome/locale/de-DE/openInBrowser.dtd
/usr/share/xul-ext/openinbrowser/chrome/locale/de-DE/openInBrowser.properties
/usr/share/xul-ext/openinbrowser/chrome/locale/en-US/
/usr/share/xul-ext/openinbrowser/chrome/locale/en-US/openInBrowser.dtd
/usr/share/xul-ext/openinbrowser/chrome/locale/en-US/openInBrowser.properties
/usr/share/xul-ext/openinbrowser/chrome/locale/fr/
/usr/share/xul-ext/openinbrowser/chrome/locale/fr/openInBrowser.dtd
/usr/share/xul-ext/openinbrowser/chrome/locale/fr/openInBrowser.properties
/usr/share/xul-ext/openinbrowser/chrome/locale/ru/
/usr/share/xul-ext/openinbrowser/chrome/locale/ru/openInBrowser.dtd
/usr/share/xul-ext/openinbrowser/chrome/locale/ru/openInBrowser.properties
/usr/share/xul-ext/openinbrowser/chrome/locale/sv-SE/
/usr/share/xul-ext/openinbrowser/chrome/locale/sv-SE/openInBrowser.dtd
/usr/share/xul-ext/openinbrowser/chrome/locale/sv-SE/openInBrowser.properties
/usr/share/xul-ext/openinbrowser/components/
/usr/share/xul-ext/openinbrowser/components/OpenInBrowser.js
/usr/share/xul-ext/openinbrowser/install.rdf