I that Firefox ESR here on portableapps is ver 60.xx
Never saw Firefox ESR 52.9.0 here & don't know if it was even created, but I could've missed it. Version 52.9.0 is from June 25 2018
Seeing that Firefox ESR 52 xxx is the last ESR version of Firefox that has support for Windows XP maybe it is a version that you should keep around for a while, for those that might be in need of it, and not only have version 60.xx which is of course incompatible with Windows XP
https://archive.mozilla.org/pub/firefox/releases/52.9.0esr/win32-sha1/en...