Mark it as resolved and have a nice day. https://ftp.mozilla.org/pub/firefox/releases/52.3.0esr/

The portable Firefox 52.3.0esr is an option as it can run in its own folder or even off a usb flash drive and not touch any current Firefox installs or its Profiles. https://sourceforge.net/projects/portableapps/files/Mozilla%20Firefox,%20Portable%20Ed./Mozilla%20Firefox%20ESR,%20Portable%20Edition%2052.3.0/ If you use the setup version of Fx 52.3.0esr and have a current Firefox then custom install them in their own folders and have them use their own Profiles and Not share the Profiles. https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles Also why do you need such an old vulnerable version as Firefox 52.0 was released way back on March 7, 2017.