Although this could go in the "browsers" thread, I didn't want this to get buried in the many pages of that thread.
After some detective work, I've located Firefox 52.9.1 ESR buried on Mozilla's servers and confirmed it works on Windows XP. The 52.9.0 version is dated 25-JUN-2018 while the 52.9.1 version is dated 06-SEP-2018.
The links are https://download-origin.cdn.mozilla.net/pub/firefox/tinderbox-builds/mozilla-esr52-win32/1536215521/firefox-52.9.1.en-US.win32.installer.exe and alternate link is https://archive.mozilla.org/pub/firefox/tinderbox-builds/mozilla-esr52-win32/1536215521/firefox-52.9.1.en-US.win32.installer.exe. I've also added it to my FTP: http://sdfox7.com/xp/sp3/EOL/firefox-52.9.1.en-US.win32.installer.exe
I'm not sure why Mozilla didn't make this release public, but ENJOY! Note that I don't use XP 64 bit but I would expect the same results.
