To download legacy versions of Firefox, such as versions 12 through 51 or the 52 ESR (Extended Support Release), you should use the official Mozilla FTP Archive
– they have unpatched critical security vulnerabilities . Use them only for: Download Firefox 12-51 52 Esr
If you are downloading for a corporate environment, avoid standard version 52.0. You want . To download legacy versions of Firefox, such as
You can find the direct installers for the versions you requested here: Firefox 52.9.0 ESR (Final v52 Release): You can find the direct installers for the
is primarily done to maintain compatibility with legacy web technologies, such as the Java NPAPI plugin or older hardware like IP cameras. 1. Key Versions & Use Cases Firefox 52 ESR (Extended Support Release): This was the final version to support Windows XP Windows Vista . It was also the last to support the NPAPI plugin , which is required for older Java-based applications. Firefox 12 to 51: