XORSelection is a 010 Editor script I wrote some time ago, and it is included in the 010 Editor script repository. You provided it with an XOR key (ASCII or HEX), and then it will XOR-encode the file (or selection) open in 010 Editor.
I discovered it will not work properly if the hexadecimal key contains a NULL byte (0x00). This is fixed in this new version.
This new version also allows whitespace characters when an hexadecimal key is provided (hexadecimal keys start with 0x).
XORSelection_V4_0.zip (https)
MD5: 1B3DB8C8DA51224DDE7CA0E4BDAAC945
SHA256: 22E60E10BC99BD24A408C12CC674858DB6F318088CD34B7C70782833401AACF2
Article Link: https://blog.didierstevens.com/2018/04/16/update-xorselection-1sc-version-4-0/