@GossiTheDog Unpopular opinion: Proof looks like web cache poisoning and not RCE. Looks like made to believe to be an actual txt file
Notice the "?" param where is used as part of cachebuster PoC for web cache poisoning
As if not, then all Archive entries should resolve to the same txt contents, however bunch 404 like the x.txt itself and there is "?a" which disproves the proof based from Archive timestamp
x.txt - 404
x.txt?mail - with email text
x.txt?a - 404
x.txt?x - with email text