Yes, this has been known for quite some time, however the original posts on it were removed following the June 2018 server crash, so allow me to post here how to get it working, since it requires special steps:
1. Download the 52.9.1 64 bit installer, linked on the list.
2. Extract it using 7zip. In the extracted folder, open the "core" subdirectory:
3. Download @blackwingcat's "Pemaker" program here. After downloading, be sure to run it as administrator, otherwise the following will not work.
4. After opening Pemaker, click the "English" checkbox, and then click on the "load" button on the main program window under the "main" tab. After doing this, browse to the "firefox.exe" file in the core subdirectory of the extracted 52.9.1 installer, and open it in Pemaker. After doing this, change the "OSVersion" and "SubSysVersion" values to 6.0 from 6.1:
5. After doing this, click on the "Save" button and save the file to a location different from the "core" subdirectory, such as your desktop. Repeat these steps for all .EXE files in the "core" directory.
6. After doing this, copy and paste all your modified .EXE files to the "core" subdirectory, replacing all original .exe files.
7. If you did everything correctly, you should now be able to run Firefox 52.9.1 ESR 64-bit just fine in Windows Vista!
I will update the Firefox list entry to include this guide.