For (the final update of that branch), use the Mozilla 52.0esr Directory.
Navigate to your platform (e.g., /win64/ for 64-bit Windows or /mac/ for macOS) and select your language (e.g., en-US ). Download Firefox 12-51 52 Esr
For Firefox 52 ESR, which was released in April 2017 and supported until August 2018, users can still find it through the following methods: For (the final update of that branch), use the Mozilla 52