Modern browsers have entirely stripped out NPAPI support. Firefox 52.9.0 ESR is the last variant that allows users to run Java applets, Silverlight applications, and legacy Adobe Flash elements required by old intranet portals.

: Do not log into sensitive personal accounts (banking, primary email, or corporate portals) using this browser.

Because this version is discontinued, Mozilla does not list it on their homepage. You must download it from the official . 1. Official Mozilla FTP Site (Recommended)