hi, firefox esr is a particular release channel only receiving security fixes - it is based on firefox 52 at the moment. the site at https://www.mozilla.org/en-US/firefox/organizations/faq/ contains a scheme how the releases in the esr cycle look in comparison to regular firefox versions.

Firefox 52 and later releases only support the Shockwave Flash plugin and disable all other plugins. If you need to use other plugins then you can use the Firefox 52 ESR release. Otherwise you can stay with the current Firefox release version.

Why-do-Java-Silverlight-Adobe-Acrobat-and-other-plugins-no longer work.

• https://support.mozilla.org/en-US/kb/npapi-plugins