Basilisk just removed the sandboxing code from its source code https://www.reddit.com/r/firefox/comments/8mankj/basilisk_just_removed_the_sandboxing_code_from/
But their Requirements page says it does NOT support XP. See at... https://www.basilisk-browser.org/requirements.shtml
You need to install one special fork by Roytam1: New build of basilisk/UXP for XP! https://msfn.org/board/topic/177125-my-build-of-new-moon-temp-name-aka-pale-moon-for-xp/?page=56 You need to unzip the 7z in your programs folder. Updates are weekly. The new 7z file must be decompressed in the same folder. Your personalizations are maintained.
Thank you for your honor. But I'm not a "Sensei", just a simple fisherman. Besides you were born before me, I am only 54 years old. See you soon my friend.
After this announcement why use Basilisk? Better to use Pale Moon. For Tobin Pale Moon it is safer than Basilisk: https://forum.palemoon.org/viewtopic.php?f=4&t=21079
https://www.mozilla.org/en-US/firefox/65.0.1/releasenotes/ they left Basilisk users close to a month unpatched... nice