: Firefox 52 ESR was the last version to support non-Flash NPAPI plugins. Versions 51 and below are often sought by users who need to maintain access to legacy web-based tools or hardware (like old webcams) that rely on these plugins. Legacy Extensions

: Select the folder for your operating system: win32/ for 32-bit Windows. win64/ for 64-bit Windows. linux-x86_64/ for 64-bit Linux.

Older Firefox versions will automatically try to update to the newest version. Go to > Options > Advanced > Update . Select "Never check for updates" . 2. Use a Dedicated Profile

Choose your preferred language folder (e.g., en-US for American English).

and select "Check for updates but let you choose whether to install them."

This is the absolute final update for the 52 series, released in June 2018 to provide the last security fixes for older operating systems. 2. Where to Download Safely